Guidable intravascular blood pump and related methods

ABSTRACT

An improved intravascular blood pump and related methods involving the broad inventive concept of equipping the intravascular blood pump with guiding features such that the intravascular blood pump can be selectively positioned at a predetermined location within the circulatory system of a patient.

RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 15/239,697, filed Aug. 17, 2016, which is a divisional ofco-pending U.S. patent application Ser. No. 15/239,574, filed Aug. 17,2016, which is a divisional of co-pending U.S. patent application Ser.No. 14/966,669, filed Dec. 11, 2015, which is a divisional of U.S.patent application Ser. No. 14/543,815, filed Nov. 17, 2014 (now U.S.Pat. No. 9,327,068, issued May 3, 2016), which is a continuation of U.S.patent application Ser. No. 12/772,810, filed May 3, 2010 (now U.S. Pat.No. 8,888,728, issued Nov. 18, 2014), which is a continuation of U.S.patent application Ser. No. 11/375,926, filed Mar. 15, 2006 (now U.S.Pat. No. 7,731,675, issued Jun. 8, 2010), which is a divisional of U.S.patent application Ser. No. 10/070,178, filed Jul. 19, 2002, (now U.S.Pat. No. 7,022,100, issued Apr. 4, 2006) which claims the benefit ofPCT/US00/24515 filed Sep. 1, 2000, which claims the benefit ofprovisional U.S. Patent Application Ser. No. 60/152,249 filed Sep. 3,1999. We hereby claim priority to the aforementioned application(s) andalso incorporate herein by reference each of the afore-listed patentsand applications in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to blood pumps and, moreparticularly, to an improved intra-vascular blood pump having a guidemechanism which provides the ability to selectively guide theintravascular pump to a desired location within a patient's circulatorysystem.

DESCRIPTION OF RELATED ART

Over the years, various types of blood pumps have been developed for thepurpose of augmenting or replacing the blood pumping action of damagedor diseased hearts. Blood pumps are commonly used in three situations:(1) for acute support during cardio-pulmonary operations; (2) forshort-term support while awaiting recovery of the heart from surgery; or(3) as a bridge to keep a patient alive while awaiting hearttransplantation. The pumps may be designed to provide right and/or leftventricular assist, although left ventricle assist is the most commonapplication in that it is far more common for the left ventricle tobecome diseased or damaged than it is for the right ventricle.

Blood pumps must provide leak-free operation and must avoidcontamination of the fluid by the pump components and the externalenvironment. Such pumps must also pump the fluid at a suitable ratewithout applying excessive Reynolds shear stress to the fluid. It iswell known to those skilled in the art that lysis or cell destructionmay result from application of shear stress to cell membranes. Red bloodcells are particularly susceptible to shear stress damage as their cellmembranes do not include a reinforcing cytoskeleton to maintain cellshape. Lysis of white blood cells and platelets also occurs uponapplication of high shear stress. Lysis of red blood cells can result inrelease of cell contents which trigger subsequent platelet aggregation.Sublytic shear stress leads to cellular alterations and directactivation and aggregation of platelets and white blood cells.

Intravascular blood pumps comprise miniaturized blood pumps capable ofbeing percutaneously or surgically introduced into the vascular systemof a patient, typically to provide left and/or right heart support. Onetype of intravascular pump is an axial flow blood pump comprising acable-mounted rotor surrounded by a protective shroud. The pump, alongwith the rotor and shroud, are mounted at the end of an elongatedflexible catheter. The catheter is inserted into the aorta from a remoteentry point, such as an incision below the groin that provides accessinto a femoral artery. The catheter then passes through the descendingaorta until it reaches the ascending aorta, near the heart. The catheterdevice encloses a rotating drive cable which is coupled to the impellerblade at one end, and which emerges from the exposed end of thecatheter, near the patient's groin, at the other end. When the exposedend of the drive cable is mechanically rotated, using a device locatedoutside the patient's body, it conveys the rotational force through thelength of the catheter, causing the impeller to spin at high speed nearthe heart. This type of blood pump finds particular application inproviding ventricular assist during surgery or providing temporarybridging support to help a patient survive a crisis.

While generally effective in providing ventricular assisting functions,prior art intravascular blood pumps nonetheless suffer variousdrawbacks. A significant drawback is that prior art intravascular bloodpumps are difficult to guide into the appropriate position within thecirculatory system of a patient. This is due largely to the fact thatthe elongated catheter is incapable of providing the degree of controlnecessary to easily negotiate the pump through the tortuous pathwaysleading up to and into the heart. When attempting to place the bloodpump in a trans-valvular configuration (with the inlet in the leftventricle and the pump outlet in the ascending aorta), the naturaltendency of the catheter to stay straight may cause the pump to beinadvertently placed in the carotid ostia, which can be dangerous if thepump is operated to withdraw blood from the brain.

To overcome these difficulties, certain guide mechanisms may be employedto assist the physician placing the pump in the appropriate positionwithin the circulatory system. One type of supplemental guide mechanismis a guide catheter. Guide catheters are designed with certainguidability characteristics such that physicians can selectivelyposition them within the vasculature or heart with relative ease. Acentral lumen is provided within the guide catheter such that theintravascular pump may be introduced therein and guided while it isadvanced towards the predetermined circulatory site. While generallyeffective at providing a guiding feature for such intravascular bloodpumps, employing such supplemental guide mechanisms is nonethelessdisadvantageous in that they consume valuable space within the vessels.A guide catheter, for example, would necessarily be larger in diameterthan the diameter of the pump and protective shroud in order to provideadequate passage of those components. As will be appreciated, thisrestricts the amount of space available for blood to flow within theparticular vessel, and increases the size of the required puncture woundfor accessing the vessel.

The present invention is directed at eliminating and/or reducing theeffects of the foregoing drawbacks of prior art intravascular bloodpumps.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of the prior art byproviding an improved intravascular blood pump equipped with integratedfeatures for selectively guiding the intravascular blood pump to apredetermined location in the patient's circulatory system, i.e. heartand/or vasculature. In so doing, the intravascular blood pump of thepresent invention eliminates the need for supplemental guidingmechanisms, such as a separate, large diameter guide catheter as used inthe prior art.

In a first broad aspect of the present invention, an intravascular bloodpump system is provided comprising an intravascular blood pump having acannula coupled thereto and an “over-the-wire” type guide mechanism forselectively positioning the intravascular blood pump and cannula at apredetermined location within the circulatory system of a patient. Toaccomplish this, a central lumen is formed through at least a portion ofthe intravascular blood pump system such that a guide element, such as aguide wire, may be progressed therethrough and advanced to thepredetermined location in the circulatory system of the patient. Afterthe guide element is advanced to this desired location, theintravascular blood pump and cannula may thereafter be advanced alongthe guide element to the desired location.

In a second broad aspect of the present invention, an intravascularblood pump system is provided comprising an intravascular blood pumphaving a cannula coupled thereto and a “side-rigger” or “rapid exchange”type guide mechanism for selectively positioning the intravascular bloodpump and cannula at a predetermined location within the circulatorysystem of a patient. To accomplish this, a side lumen is formed along alength of at least one of the intravascular blood pump and the cannula.A guide element, such as a guide wire, may be advanced to thepredetermined location in the circulatory system of the patient. Afterthe guide element is advanced to this desired location, theintravascular blood pump and cannula may thereafter be advanced alongthe guide element to the desired location.

In a third broad aspect of the present invention, an intravascular bloodpump system is provided comprising an intravascular blood pump having acannula coupled thereto and a “guide catheter” type guide mechanism forselectively positioning the intravascular blood pump and cannula at apredetermined location within the circulatory system of a patient. Thepump system of this broad aspect includes a conduit assembly and aseparate pump assembly. The conduit assembly includes a guide catheter,a rotor shroud, and a cannula, with the cannula and guide catheterdisposed on either side of the rotor shroud. The pump assembly includesa rotor, a drive member coupled to the rotor, and a pump disposedbetween the rotor and the drive member. The guide catheter isdimensioned to receive and guide the pump assembly to the point wherethe rotor docks within the rotor shroud so as to form an operationalblood pump. This configuration allows the conduit assembly to beprecisely and efficiently guided into a desired position within the bodythrough the use of conventional guiding techniques well known ininterventional cardiology. The pump assembly may thereafter beintroduced into and guided within the conduit until the pump assembly isdocked within the rotor shroud. This dual construction arrangementprovides improved placement of the pump assembly by using the conduit asa guiding mechanism.

The foregoing broad aspects of the present invention may be manifestedaccording to the following recitations:

According to a first broad recitation of the present invention, anintravascular blood pump system is provided comprising an intravascularblood pump having a cannula coupled thereto, and a guide mechanismadapted to guide the intravascular blood pump and cannula to apredetermined location within the circulatory system of a patient.

In a further embodiment, the intravascular blood pump includes a rotor,a shroud for receiving the rotor, and a drive cable coupled to the rotorfor driving the rotor within the shroud.

In a further embodiment, the cannula is coupled to the shroud of theintravascular blood pump.

In a further embodiment, the guide mechanism comprises a guide cathetercoupled to the shroud.

In a further embodiment, the guide catheter may be used to guide theshroud and cannula to the predetermined location within the circulatorysystem of the patient, after which point the rotor and drive cable ofthe intravascular blood pump may be docked within the shroud for pumpoperation.

In a further embodiment, the drive cable sheath is provided having acentral lumen for receiving the drive cable, and wherein a purge fluiddelivery system is coupled to the drive cable sheath to deliver purgefluid to the rotor.

In a further embodiment, the drive cable sheath includes at least oneside lumen for delivering the purge fluid towards the rotor.

In a further embodiment, a portion of the purge fluid is deliveredthrough the at least one side lumen and past the rotor, and a portion ofpurge fluid is rerouted back from the rotor through the central lumen ofthe drive cable.

In a further embodiment, a perfusion assembly is providedcommunicatively coupled to the guide catheter for selectively reroutingblood from within the guide catheter to a point downstream from theintroduction site of the guide catheter into the vasculature of thepatient.

In a further embodiment, the perfusion assembly includes a first conduitcommunicatively coupled to the guide catheter, a second conduitdimensioned to be introduced into the vasculature of the patient, and aselectively operable valve disposed in between the first conduit and thesecond conduit.

In a further embodiment, a blood pressure detection mechanism isprovided to detect the pressure of the blood proximate at least one ofthe intravascular blood pump and cannula.

In a further embodiment, the blood pressure detection mechanismcomprises at least one of fluid filled column disposed within at least aportion of the cannula, a piezoelectric element coupled to at least oneof the intravascular blood pump and cannula, and a strain gauge coupledto at least one of the intravascular blood pump and cannula.

In a further embodiment, the blood pressure detection mechanism involvescalculating blood pressure based on the relationship between the torqueand motor current of a motor used to drive the rotor.

In a further embodiment, the guide mechanism comprises a guide elementdisposed at least partially within the cannula.

In a further embodiment, the guide element comprises a guide wire forpassage through a side lumen formed in the cannula.

In a further embodiment, the guide element comprises a selectivelydeformable element disposed at least partially within the cannula.

In a further embodiment, the intravascular blood pump and cannula may beselectively advanced to the predetermined location within thevasculature of the patient by first passing the guide wire to thepredetermined location and thereafter sliding the intravascular bloodpump and cannula along the guide wire to the predetermined location.

In a further embodiment, the guide element comprises a guide wire forpassage through a lumen extending through the drive cable and rotor.

In a further embodiment, the intravascular blood-pump and cannula may beselectively advanced to the predetermined location within thevasculature of the patient by first passing the guide wire to thepredetermined location and thereafter sliding the intravascular bloodpump and cannula along the guide wire to the predetermine location.

In a further embodiment, the guide mechanism further includes guideelement for passage through the guide catheter to facilitate placementof the shroud and the cannula at the predetermined location within thevasculature of the patient.

In a further embodiment, the guide mechanism further includes a guideelement for passage through a side lumen formed along at least a portionof the guide catheter.

In a further embodiment, the guide element comprises at least one of aguide wire and a balloon catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a partial sectional view of a human heart illustrating anintravascular blood pump system having an “over-the-wire” type guidemechanism according to a first broad aspect of the present inventionpositioned, by way of example, in a trans-valvular configuration toprovide left-heart assist;

FIG. 2 is side view of the guidable intravascular blood pump system ofthe type shown in FIG. 1 including a motor coupler and purge fluiddelivery system according to an exemplary embodiment of the presentinvention;

FIG. 3 is a cross-sectional view illustrating an exemplary constructionof the blood pump, drive cable assembly, and cannula of theintravascular blood pump system according to the first broad aspect ofthe present invention;

FIG. 4 is a cross-sectional view taken along lines 4-4 of FIG. 3illustrating an exemplary construction of the drive cable assembly andguide mechanism according to the first broad aspect of the presentinvention;

FIG. 5 is a cross-sectional view illustrating an exemplary constructionof the motor coupler and purge fluid delivery system according to thefirst broad aspect of the present invention;

FIG. 6 is a partial sectional view of a human heart illustrating anintravascular blood pump system having a “rapid exchange” or“side-rigger” type guide mechanism according to a second broad aspect ofthe present invention positioned, by way of example, in a trans-valvularconfiguration to provide left-heart assist;

FIG. 7 is side view of the guidable intravascular blood pump system ofthe type shown in FIG. 6 including a motor coupler and purge fluiddelivery system according to an exemplary embodiment of the presentinvention;

FIG. 8 is a cross-sectional view taken along lines 8-8 of FIG. 7illustrating the “side-rigger” or “rapid exchange” type guide mechanismaccording to the second broad aspect of the present invention;

FIG. 9 is a cross-sectional view of the type shown in FIG. 8illustrating an alternate configuration of the guide mechanism accordingto the second broad aspect of the present invention;

FIG. 10 is a partial sectional view of a human heart illustrating anintravascular blood pump system having a “guide catheter” type guidemechanism according to a third broad aspect of the present inventionpositioned, by way of example, in a trans-valvular configuration toprovide left-heart assist;

FIG. 11 is a schematic view of a human being illustrating theintravascular blood pump system of the type shown in FIG. 10 insertedthrough the femoral artery and including an optional perfusion assemblyfor perfusing the vasculature downstream from the incision site whereguide catheter enters the femoral artery;

FIG. 12 is a side view of the intravascular blood pump system shown inFIGS. 10-11 illustrating the separable nature of a pump assembly and aconduit assembly which collectively form the intravascular blood pumpsystem according to the third broad aspect of the present invention;

FIG. 13 is a side view illustrating the intravascular blood pump systemshown in FIG. 12 with the pump assembly docked into the conduit assemblyaccording to the third broad aspect of the present invention;

FIG. 14 is a cross-sectional view illustrating an exemplary constructionof the blood pump, drive cable assembly, cannula, and guide catheter ofthe intravascular blood pump system shown in FIG. 13;

FIG. 15 is a cross-sectional view taken along lines 15-15 of FIG. 14illustrating an exemplary construction of the drive cable assembly andguide catheter according to the third broad aspect of the presentinvention;

FIG. 16 is a cross-sectional view illustrating an exemplary constructionof the motor coupler, purge fluid delivery system, and a proximalportion of the guide catheter biasing assembly according to the thirdbroad aspect of the present invention;

FIG. 17 is a cross-sectional view illustrating an exemplary constructionof the perfusion assembly and a distal portion of the guide catheterbiasing assembly according to the third broad aspect of the presentinvention;

FIG. 18 is a cross-sectional view of an intravascular blood pump systemof the type shown in FIGS. 12-13 having an alternate configuration fordocking the rotor within the shroud according to the principles of thepresent invention; and

FIG. 19 is a partial sectional view of a human heart illustrating analternate intravascular blood pump system having an “over-the-wire” typeguide mechanism according to the first broad aspect of the presentinvention positioned, by way of example, in a trans-valvularconfiguration to provide right-heart assist.

FIG. 20 corresponds to FIG. 1 of U.S. Ser. No. 09/280,988, and is aschematic side view of a steerable cannula in the undeformed state inaccordance with the first embodiment of U.S. Ser. No. 09/280,988;

FIG. 21 corresponds to FIG. 2 of U.S. Ser. No. 09/280,988, and is aschematic cross-sectional view of the steerable cannula of FIG. 20 takenalong line 2-2;

FIG. 22 corresponds to FIG. 3 of U.S. Ser. No. 09/280,988, and is aschematic side view of the steerable cannula in the deformed state inaccordance with the first embodiment of U.S. Ser. No. 09/280,988;

FIG. 23 corresponds to FIG. 4 of U.S. Ser. No. 09/280,988, and is aschematic cross-sectional view of a steerable cannula having two cablesin accordance with a second embodiment of U.S. Ser. No. 09/280,988;

FIG. 24 corresponds to FIG. 5 of U.S. Ser. No. 09/280,988, and is aschematic side view of a steerable cannula having a reinforcing wire inaccordance with a third embodiment of U.S. Ser. No. 09/280,988;

FIG. 25 corresponds to FIG. 6 of U.S. Ser. No. 09/280,988, and is aschematic cut-away view of a steerable cannula in accordance with afourth embodiment of U.S. Ser. No. 09/280,988;

FIG. 26 corresponds to FIG. 7 of U.S. Ser. No. 09/280,988, and is aschematic cross-sectional view taken along line 7-7 of FIG. 25;

FIG. 27 corresponds to FIG. 8 of U.S. Ser. No. 09/280,988, and is aschematic side view of a steerable cannula having a preformed curve andan inflatable balloon formed at a distal end thereof in accordance witha fifth embodiment of U.S. Ser. No. 09/280,988;

FIG. 28 corresponds to FIG. 9 of U.S. Ser. No. 09/280,988, and is aschematic side view of the inflatable balloon of a fifth embodiment ofU.S. Ser. No. 09/280,988, wherein the balloon is shown in the inflatedstate;

FIG. 29 corresponds to FIG. 10 of U.S. Ser. No. 09/280,988, and is aschematic cross-sectional view taken along line 10-10 of FIG. 28;

FIG. 30 corresponds to FIG. 11 of U.S. Ser. No. 09/280,988, and is aschematic view showing a steerable cannula having a pigtail distal tipconfiguration in accordance with a sixth embodiment of U.S. Ser. No.09/280,988;

FIG. 31 corresponds to FIG. 12 of U.S. Ser. No. 09/280,988, and is aschematic view showing a steerable cannula having a guidewire distal tipconfiguration in accordance with a seventh embodiment of U.S. Ser. No.09/280,988;

FIG. 32 corresponds to FIG. 13 of U.S. Ser. No. 09/280,988, and is aschematic view showing a steerable cannula having a guidewire distal tipconfiguration in accordance with an eighth embodiment of U.S. Ser. No.09/280,988;

FIG. 33 corresponds to FIG. 14 of U.S. Ser. No. 09/280,988, and is aschematic side view showing a steerable cannula used in a co-axialconfiguration in accordance with a ninth embodiment of U.S. Ser. No.09/280,988, wherein the steerable cannula is advanced to a firstrelative position;

FIG. 34 corresponds to FIG. 15 of U.S. Ser. No. 09/280,988, and is aschematic side view showing a steerable cannula of FIG. 33, wherein thesteerable cannula is advanced to a second relative position; and

FIG. 35 corresponds to FIG. 16 of U.S. Ser. No. 09/280,988, and is aschematic side view of a configuration in accordance with a tenthembodiment of U.S. Ser. No. 09/280,988.

FIG. 36 corresponds to FIG. 1 of U.S. Ser. No. 09/280,970, and is aschematic side view of a first embodiment of U.S. Ser. No. 09/280,970;

FIG. 37 corresponds to FIG. 2 of U.S. Ser. No. 09/280,970, and is aschematic cross-sectional view taken along line 2-2 of FIG. 36;

FIG. 38 corresponds to FIG. 3 of U.S. Ser. No. 09/280,970, and is aschematic cross-sectional view taken along line 3-3 of FIG. 36;

FIG. 39 corresponds to FIG. 4 of U.S. Ser. No. 09/280,970, and is aschematic view of a cannula in accordance with an embodiment in asurgical application;

FIG. 40 corresponds to FIG. 5 of U.S. Ser. No. 09/280,970, and is aschematic partial cut-away side view of a second embodiment of U.S. Ser.No. 09/280,970;

FIG. 41 corresponds to FIG. 6 of U.S. Ser. No. 09/280,970, and is aschematic cross-sectional view taken along line 6-6 of FIG. 40;

FIG. 42 corresponds to FIG. 7 of U.S. Ser. No. 09/280,970, and is aschematic side view of a third embodiment of U.S. Ser. No. 09/280,970;

FIG. 43 corresponds to FIG. 8 of U.S. Ser. No. 09/280,970, and is aschematic side view of a fourth embodiment of U.S. Ser. No. 09/280,970;

FIG. 44 corresponds to FIG. 9 of U.S. Ser. No. 09/280,970, and is aschematic side view of a fifth embodiment of U.S. Ser. No. 09/280,970;

FIG. 45 corresponds to FIG. 10 of U.S. Ser. No. 09/280,970, and is aschematic side view of a sixth embodiment of U.S. Ser. No. 09/280,970;

FIG. 46 corresponds to FIG. 11 of U.S. Ser. No. 09/280,970, and is aschematic cross sectional view taken along line 11-11 of FIG. 45;

FIG. 47 corresponds to FIG. 12 of U.S. Ser. No. 09/280,970, and is aschematic side view of a seventh embodiment of U.S. Ser. No. 09/280,970;

FIGS. 48 and 49 correspond to FIGS. 13 and 14, respectively, of U.S.Ser. No. 09/280,970, and are schematic side views of an eighthembodiment of U.S. Ser. No. 09/280,970;

FIG. 50 corresponds to FIG. 15 of U.S. Ser. No. 09/280,970, and is aschematic cross-sectional view taken along line 15-15 of FIG. 49;

FIG. 51 corresponds to FIG. 16 of U.S. Ser. No. 09/280,970, and is aschematic side view of a ninth embodiment of U.S. Ser. No. 09/280,970;

FIG. 52 corresponds to FIG. 17 of U.S. Ser. No. 09/280,970, and is aschematic side view of a tenth embodiment of U.S. Ser. No. 09/280,970;

FIG. 53 corresponds to FIG. 18 of U.S. Ser. No. 09/280,970, and is aschematic cross-sectional view taken along line 18-18 of FIG. 52; and

FIG. 54 corresponds to FIG. 19 of U.S. Ser. No. 09/280,970, and is aschematic side view of an eleventh embodiment of U.S. Ser. No.09/280,970.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation may bedescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present invention involves an intravascular pump system for use in anumber of broad ranging applications involving the augmentation of bloodflow within the circulatory system of a patient. As will be describedbelow, the intravascular blood pump system of the present inventionovercomes the drawbacks of the prior art by providing a guide mechanismas part of the intravascular blood pump. This advantageously allows theintravascular blood pump to be selectively guided to a predeterminedlocation within the circulatory system of a patient without the need forbulky supplemental guide mechanisms, such as a separate guide catheter.

The intravascular pump assembly of the present invention is particularlysuited for trans-valvular use, such as for left and/or right ventricularassist procedures. By way of example only, such ventricular assistprocedures may be employed in cardiac operations including, but notlimited to, coronary bypass graft (CABG), cardio-pulmonary bypass (CPB),open chest and closed chest (minimally invasive) surgery,bridge-to-transplant and/or failure-to-wean-from-bypass situations. Itis to be readily understood, however, that the intravascular blood pumpassembly and methods of the present invention are not to be limited tosuch applications. Moreover, while illustrated and described largelywith reference to left-heart assist applications, it is to be readilyunderstood that the principles of the present invention apply equallywith regard to right-heart assist application, which are contemplated aswithin the scope of the present invention. These and other variationsand additional features will be described throughout.

Referring to FIG. 1, shown is a guidable intra-vascular blood pumpsystem 10 according to a first broad aspect of the present inventionshown, by way of example only, in a left-heart assist configurationwithin a human heart. The system 10 includes an intravascular blood pump12, a cannula 14, and an “over-the-wire” type guide mechanism 16. Adrive cable assembly 18 and a motor assembly 20 are provided to drivethe intravascular blood pump 12. The “over-the-wire” guide mechanism 16comprises a suitable guide element dimensioned to pass slideably througha central lumen extending through the drive cable 18, blood pump 12, andcannula 14. Suitable guide elements may include any number ofconventional guiding devices, including but limited to those employed incardiology. By way of example only, the guide element is shown as aguide wire 22. According to the present invention, the “over-the-wire”guide mechanism 16 provides the ability to selectively guide the bloodpump 12 and cannula 14 to a predetermined position in the circulatorysystem of a patient, such as the trans-valvular position shown.

To accomplish this, the guide wire 22 is first introduced into thevascular system of a patient through any suitable access point, such asthrough the use of the well known Seldinger technique. The guide wire 22can then be advanced within the patient to a desired location within thecirculatory system of the patient. This may be done using the controlfeatures of the guide wire 22 itself, or may be facilitated through theuse of any number of supplemental guidance mechanisms or techniques toensure the proper and efficient placement of the guide wire 22. Suchsupplemental guidance techniques may include, but are not necessarilylimited to, guide catheters and/or techniques involving ultra-sound orfluoroscopy. Once the guide wire 22 is positioned at the desiredlocation (such as in left ventricle as shown), the blood pump 12 andcannula 14 may thereafter be advanced along the guide wire 22 andpositioned in the trans-valvular configuration shown. Under theoperation of the motor assembly 20, the blood pump 12 may be used forleft-heart assist by selectively withdrawing blood from the leftventricle (through the interior of the cannula 14) for delivery outwardthrough outflow apertures formed in the blood pump 12. This outflow fromthe blood pump 12 flows along the exterior of the drive cable assembly18 in a substantially axial fashion for arterial distribution throughoutthe body.

Referring to FIGS. 2-5, an exemplary embodiment of the intravascularblood pump system 10 of FIG. 1 will now be described. As shown in FIG.2, the intravascular blood pump system 10 includes a coupler 24 and, aswill be described in greater detail below, a purge fluid delivery system26 for providing a two-way fluid flow within the drive cable assembly 18during pump operation. The purge fluid delivery system 26 includes afluid inlet conduit 28 for introducing pressurized purge fluid from afluid source (not shown) for delivery into the blood pump 12, and afluid outlet conduit 30 to withdraw a return flow of purge fluid fromthe blood pump 12. The motor coupler 24 establishes a mechanicalconnection between a motor (not shown) and a drive cable (not shown) forproviding motive force to the blood pump 12 for pump operation. Thedrive cable assembly 18 includes a drive cable sheath 32 which, inaddition to serving a purge fluid delivery function, also serves as aprotective housing for the drive cable (not shown). Although shown inbroken form for clarity, it will be appreciated that the drive cableassembly 18 (and all components thereof) may be provided in any suitablelength sufficient for intravascular applications. That is to say, thelength of the drive cable assembly 18 must be enough to reach betweenthe motor coupler 24 and purge fluid delivery system 26, located outsidethe patient, and the desired location within the patient's circulatorysystem where the blood pump 12 is to be positioned.

The intravascular blood pump 12 is shown (by way of example only) as anaxial flow intravascular blood pump. The blood pump 12 includes pumpbody 34, a rotor shroud 36 having flow ports 38, and an internallydisposed rotor (not shown) having a shaft rotatably disposed within thepump body 34 and an impeller rotatably disposed within the rotor shroud36. The cannula 14 is fixedly attached to the rotor shroud 36 and mayextend any suitable length therefrom depending upon the particularintravascular application. The cannula 14 preferably includes aplurality of ports or fenestrations 40 about its distal region, as wellas an end port 42, which allow for the ingress or egress of blood intoor from the cannula 14 depending upon the operation of the blood pump12. That is to say, if the pump 12 is configured for left-heart assistas shown in FIG. 1, then the ports 40, 42 will allow the ingress ofblood into the cannula 14 from the left ventricle. If, on the otherhand, the blood pump 12 is configured for right-heart assist (i.e. withthe pump 12 in the right atrium and the distal end of the cannula 14located within the pulmonary artery), then the ports 40, 42 will allowthe egress of blood from the cannula 14 into the pulmonary artery.(Details on right-heart assist applications will be discussed in greaterdetail below.) The pump 12 and cannula 14 may be dimensioned to anysuitable diameter for intravascular applications. For example, the rangeof sizes may include, but is not necessarily limited to, 9 French to 30French, although the range is more preferably from 14 French to 24French, and most preferably from 18 French to 20 French.

The “over-the-wire” type guide mechanism 16 includes the guide wire 22and, as will be explained in greater detail below, a central lumenextending through the cannula 14, blood pump 12, drive cable assembly18, purge fluid delivery system 26, and motor coupler 24. As notedabove, the central lumen is dimensioned to slideably receive the guidewire 22 such that the blood pump 12 and cannula 14 may be slideablyadvanced along the guide wire 22 to a desired location within thecirculatory system of a patient after the guide wire 22 has been sopositioned using conventional guidance techniques. It is to be readilyunderstood that, while shown as a conventional guide wire 22, the guideelement forming part of the guide mechanism 16 of the present inventionmay include any number of well known guidance mechanisms depending uponthe application, including but not limited to balloon catheters, imagingwires, and guide catheters dimensioned to be slideably received throughthe central lumen. For example, although not appropriate for retrogradeprogression (such as the left-heart application shown in FIG. 1), aballoon catheter may be a suitable guidance mechanism for a right-heartassist application. In such a case, the balloon may be inflated and usedas a “sail” to direct the catheter to a desired location (such as thepulmonary artery), after which point the blood pump 12 and cannula 14can be advanced over the catheter to a trans-valvular configuration withthe blood pump 12 in the right atrium and the ports 38, 40 of thecannula 14 in the pulmonary artery.

FIGS. 3 and 4 further detail the construction of the blood pump 12,cannula 14, drive cable assembly 18, and “over-the-wire” guide mechanism16. The blood pump 12 includes a rotor 44 having a shaft 46 and animpeller 48. The shaft 46 is rotatably disposed within the pump body 34via a bearing pack comprising, by way of example, ball bearingassemblies 50, 52 and spring 54. Ball bearings assemblies 50, 52 arewell known in the art, each comprising an inner race which rotates alongwith the rotor shaft 46, an outer race which remains in a static andfixed position against the inner surface of the pump body 34, and aplurality of ball bearings disposed between the inner and outer races.The spring 54 biases each bearing assembly 50, 52 axially away from oneanother to reduce axial play during pump operation. The shaft 46 isgenerally hollow and dimensioned to receive a cable adapter 60 thereinfor the purpose of coupling the rotor 44 to a drive cable 62 formingpart of the drive cable assembly 18. The drive cable 62 may be securedto the cable adapter 60 in any number of suitable fashions, includingbut not limited to the use of adhesives, crimping, and laser welding.These same techniques may be used to secure the cable adapter 60 withinthe shaft 46 of the rotor 44. A radial seal 64 is provided in betweenthe wall of the pump body 34 and a distal stepped region 66 on the rotorshaft 46, the function of which will be described below.

The impeller 48 includes a hub 56 and a plurality of blades 58 extendingtherefrom. The hub 56 is generally conical and, according to the firstbroad aspect of the present invention, is hollow throughout to form partof the central lumen of the guide mechanism 16. In this regard, the hub56 is preferably provided with a gasket or seal member 68 at its distaltip. The seal member 68 may be made of any suitable sealing material(including but not limited to silicone) such that the pump 12 andcannula 14 may be easily progressed along the guide wire 22 for deliveryto a desired circulatory site. The seal member 68 should also be robustenough to prevent the ingress of blood into the interior of the rotorhub 56 during pump operation, whether the guide wire 22 remains in placeor is fully withdrawn. The blades 58 are dimensioned to reside in closetolerance with the interior surface of the shroud 36. In operation, theblades 58 impart both an axial and radial vector on the blood whichcauses it to flow outward through the flow ports 38 formed in the shroud36. As used herein, the term “axial flow” is deemed to include flowcharacteristics like that shown in FIG. 3, which include both an axialand slight radial component. It is to be readily appreciated that,although shown as an axial flow type, blood pump 12 may comprise anynumber of suitable types of intravascular blood pumps, including but notlimited to so-called “mixed flow” intravascular blood pumps withoutdeparting from the scope of the present invention.

The cannula 14 is coupled at its proximal end to the rotor shroud 36.This may be accomplished in any number of fashions, including but notlimited to the use of adhesives. This may also be facilitated bydimensioning the shroud 36 to include a narrow inlet region 70 capableof being received flushly within the proximal end of the cannula 14. Theinlet region 70 of the shroud 36 should preferably have a taperedinterior surface for establishing a smooth flow transition between thecannula 14 and the region containing the impeller blades 58. Althoughshown as a single integral element, it is to be understood that the pumpbody 34 and shroud 36 may comprise two separate (and sometimesseparable) components, the significance of which will become apparentbelow. The pump body 34 and shroud 36 may be constructed from any numberof suitable materials, including but not limited to stainless steel orother medical grade compositions or alloys. The cannula 14 may also beconstructed from any number of suitable materials, including but notlimited to medical grade plastics. As shown, the cannula 14 may also befortified with spiral-wound reinforcement wire 72 within the walls ofthe cannula 14.

The drive cable assembly 18 includes the drive cable 62 and the drivecable sheath 32. The drive cable 62 is coupled to the rotor 44 via thecable adapter 60. The drive cable sheath 32 includes a central lumen 74and a plurality of side lumens 76. The central lumen 74 serves as aprotective covering for the drive cable 62. The central lumen 74, alongwith the side lumens 76, also forms part of the purge fluid deliverysystem 26 shown above in FIG. 2, which will be described in greaterdetail below. The side lumens 76 are provided in fluid communicationwith the fluid inlet conduit 28, while the central lumen 74 is providedin fluid communication with the fluid outlet conduit 30. The side lumens76 are thus configured to deliver purge, fluid into the pump 12, whilethe central lumen 74 is configured to transport purge fluid away fromthe pump 12 along the length of the drive cable 62.

The pressurized purge fluid within the side lumens 76 may take one oftwo flow paths upon entry into the pump 12. One flow path passes throughthe interior of the pump 12 and onward past the radial seal 64 toprevent the ingress of blood into the pump body 34 during pumpoperation. More specifically, the purge fluid flows distally around thecable adapter 60, through the ball bearing assemblies 50, 52, and onwardpast the radial seal 64. This egress of purge fluid past the radial seal64 can be controlled to effectively thwart the ingress of blood past theradial seal 64, which might otherwise cause clotting and/or pump damage.The other flow path is directed back out the central lumen 74 fordelivery to the fluid outlet conduit 30. In so doing, this flow pathbathes the components of the pump 12 and/or drive cable 62 and therebyreduces frictional heating within the pump 12 and/or the central lumen74 of the sheath 32 during pump operation.

The “over-the-wire” guide mechanism 16 includes a central lumen throughwhich the guide wire 22 may extend for the purpose of slideablyadvancing the blood pump 12 and cannula 14 into a desired positionwithin the circulatory system of a patient. In the embodiment shown,this central lumen is established by forming and co-aligning theindividual central lumens within each of the drive cable 62, the cableadapter 60, the shaft 46 and hub 56 of the rotor 44, and the cannula 14.In this regard, the drive cable 62 is preferably of wound-wireconstruction having a central lumen formed therein. The central lumenswithin the cable adapter 60, rotor 44, and gasket 68 may be formed viamachining or molding processes. These central lumens should preferablybe sized such that they permit the slideable passage of the pump 12 andcannula 14 therealong, but do not interfere with or constrain the guidewire 22 to cause inadvertent rotation of the guide wire 22 during pumpoperation. As noted above, it is also contemplated to remove the guidewire 22 after the pump 12 and cannula 14 are properly positioned in thepatient. In this case, the gasket or seal 68 on the hub 56 should berobust enough to reseal after the guide wire 22 is withdrawn and preventthe ingress of blood into the interior of the rotor 44.

Referring to FIG. 5, the motor coupler 24 includes a housing 78, a driveshaft adapter 80, and a bearing assembly 82. The drive shaft adapter 80includes a drive shaft coupler 84 dimensioned to receive a drive shaftof a motor (not shown), and a drive cable coupler 86 dimensioned toreceive the drive cable 62. Any of a variety of attachment techniquesmay be employed to securely fasten the drive cable 62 to the drive cablecoupler 86, including but not limited to adhesives, crimping, and laserwelding. The drive shaft adapter 80 is rotatably disposed within thehousing 78 by the bearing assembly 82. The bearing assembly 82 includesa sleeve 88 (which may alternatively be formed as an integral part ofthe housing 78) for retaining a pair of ball bearing assemblies 90, 92and a spring 94 of the type described above. That is, each bearingassembly 90, 92 generally comprises an inner race which rotates alongwith the drive shaft adapter 80, an outer race which remains in a staticand fixed position against the inner surface of the retaining sleeve 88,and a plurality of ball bearings disposed between the inner and outerraces. The spring 94 is provided to bias each bearing assembly 90, 92axially away from one another to reduce axial play during operation.

The purge fluid delivery system 26 includes a housing 96 having acentral lumen 98, an inflow port 100, and an outflow port 102. Thehousing 96 is also dimensioned to matingly receive a portion of themotor coupler 24. In this regard, a seal element 104 is providedsandwiched in between the housing 96 and housing 78 and including anaperture which extends about the drive shaft adapter 80 as it exits thehousing 78 to prevent the ingress of purge fluid into the motor coupler24. A fluid guide structure 106 is also provided within the centrallumen 98 for the purpose of separating the inflow and outflow ports 100,102. The fluid guide structure 106 includes a central lumen 108 throughwhich the drive cable 62 extends, and an elevated portion 110 thatretains an O-ring 112 against the inner surface of the central lumen 98of the housing 96. The drive cable sheath 32 is secured to the housing96 such that the inflow port 100 is communicatively coupled to the sidelumens 76, and the outflow port 102 is communicatively coupled to thecentral lumen 74. In this fashion, pressurized purge fluid may beintroduced through the inflow port 100 via inflow conduit 28, andremoved through the outflow port 102 via outflow conduit 30. By way ofexample, the inflow conduit 28 and outflow conduit 30 may be coupled totheir respective ports 100, 102 via barbed connectors 114. Similarly,the inflow and outflow conduits 28, 30 may be equipped with any numberof suitable connectors (such as those illustrated by way of example inFIG. 2) for establishing fluid communication with a source ofpressurized fluid (not shown). The pressurized fluid source (not shown)may include, but is not necessarily limited to, the use of a syringe, anindeflator, a fluid delivery pump, or an accumulator arrangement toprovide the requisite delivery of pressurized fluid. The purge fluiddelivery system 26 thus provides a two-way transmission of purge fluidwithin the drive cable sheath 32 for the purposes of cooling the bloodpump 12 and preventing the ingress of blood past the radial seal 64 andinto blood pump 12.

Referring to FIG. 6, shown is a guidable intra-vascular blood pumpsystem 120 according to a second broad aspect of the present invention.As will be described hereinafter, the intravascular blood pump system120 differs from the intravascular blood pump system 10 described aboveonly as to the type of guide mechanism employed. In the interest ofclarity and consistency, then, like reference numerals will be used todenote like elements and distinctions pointed out where necessary.Moreover, due to the commonality of principles employed in bothintravascular blood pump systems 10, 120, a discussion to the level ofdetail set forth above is not deemed necessary with regard to theintravascular blood pump system 120. Instead, those aspects in commonwith the intravascular blood pump 10 are hereby incorporated into thediscussion of the intravascular blood pump system 120.

In its most general form, the intravascular blood pump system 120 ofthis second broad aspect of the present invention comprises the bloodpump 12 and cannula 14 arrangement, wherein the cannula 14 is equippedwith a “side-rigger” or “rapid exchange” guide mechanism 122. In animportant aspect of the present invention, the “rapid exchange” or“side-rigger” guide mechanism 122 includes a guide carriage 124 formedalong at least a portion of the cannula 14, and a suitable guide element(such as guide wire 22) dimensioned to pass slidably through a lumen(not shown) extending through the guide carriage 124. The “rapidexchange” guide mechanism 122 thereby provides the ability toselectively guide the blood pump 12 and cannula 14 to a predeterminedposition in the circulatory system of a patient in the manner describedabove. Namely, the guide wire 22 may be first introduced into thevascular system of a patient through any suitable access point andguided to a desired location within the circulatory system of thepatient, i.e. the left ventricle as shown. The blood pump 12 and cannula14 may thereafter be advanced along the guide wire 22 and positioned inthe trans-valvular configuration shown for providing left-heart assist.

FIGS. 7-9 further illustrate the “side-rigger” or “rapid-exchange” guidemechanism 122 of this second broad aspect of the present invention. In apreferred embodiment, the “side-rigger” guide mechanism 122 includes alumen 126 formed within the guide carriage 124. The guide carriage 124is preferably formed as an integral extension of the wall of the cannula14. FIGS. 7 and 8 comport with the embodiment shown in FIG. 6, namelyillustrating the guide carriage 124 formed along the exterior surface ofthe cannula 14. FIG. 9 illustrates an alternate embodiment wherein theguide carriage 124 may be formed along the interior surface of thecannula 14. In either case, the guide wire 22 is advanced to a desiredlocation in the vasculature of the patient, after which point the bloodpump 12 and cannula 14 can be slidably advanced therealong for deliveryto the desired location according to the present invention. The guidewire 22 may thereafter be withdrawn from the patient. If the guidecarriage 124 is formed along the exterior surface of the cannula 14 (asshown in FIGS. 7-8), then the cannula 14 should preferably be positionedso that the guide carriage 124 does not extend in a trans-valvularfashion. For example, with reference to FIG. 6, the guide carriage 124should be positioned wholly within the left ventricle such that thepulsatile blood flow during beating heart procedures will notinadvertently pass through the side lumen 126 and pass through theaortic valve.

The intravascular blood pump system 120 is constructed in virtually thesame manner as the intravascular blood pump system 10 shown anddescribed above, with the exception of the location of the respectiveguide mechanisms 16, 122. More specifically, because the guide mechanism122 is disposed along the side of the cannula 14, there is no need toform a central lumen extending through the blood pump 12, drive cableassembly 18, purge fluid delivery system 26, and motor coupler 24 asdetailed above with regard to the intravascular blood pump system 10. Assuch, these components need not be specially machined or molded toinclude such central lumens as was required with the intravascular bloodpump system 10 set forth above.

Referring to FIG. 10, shown is a guidable intravascular blood pumpsystem 130 according to a third broad aspect of the present invention.Again, due to the commonality between many of the same components andfeatures of the intravascular blood pump systems described above and theintravascular blood pump system 130, like reference numerals will beused to denote like elements and distinctions pointed out wherenecessary. As will be explained in greater detail below, theintravascular blood pump system 130 employs yet another unique anduseful guide mechanism according to the present invention. However,because many of the same components are employed, a discussion to thelevel of detail set forth above is not deemed necessary with regard tothe intravascular blood pump system 130. Instead, those aspects incommon with the intravascular blood pumps described above are herebyincorporated into the discussion of the intravascular blood pump system130.

In its most general form, the intravascular blood pump system 130 ofthis third broad aspect of the present invention comprises the bloodpump 12 and cannula 14 arrangement, wherein a “guide catheter” 132 isprovided as the guide mechanism for positioning the pump 12 and cannula14 at a desired location within the circulatory system of the patient.More specifically, with brief reference to FIG. 12, the intravascularblood pump system 130 is formed in two separate assemblies according tothe present invention: a conduit assembly 134 and pump assembly 136. Inits most basic form, the conduit assembly 134 comprises the guidecatheter 132 and cannula 14 coupled to the rotor shroud 36. The pumpassembly 136 is constructed such that the pump body 34 and rotor 44 canbe disengaged from the rotor shroud 36 and removed entirely from theconduit assembly 134. Referring again to FIG. 10, this dual constructionforms a significant feature of the present invention because it providesthe ability to form the blood pump 12 at a desired location in a patientusing two separate and distinct steps. The first step involvespositioning the conduit assembly 134 (with the pump assembly 136removed) within a patient such that the shroud 36 and cannula 14 areeach disposed in a desired location, such as a trans-valvularconfiguration for cardiac assist procedures. In an important aspect, thetask of positioning the conduit assembly 134 within the patient may beadvantageously facilitated through the use of any number of well knownguidance mechanisms, including but not limited to guide wires, ballooncatheters, imaging wires, guide catheters, and/or techniques involvingultra-sound or fluoroscopy. The second step in providing theintravascular blood pump system 130 of the present invention involvesadvancing the pump assembly 136 through the conduit assembly 134 suchthat the rotor 44 docks within the shroud 36 to form the pump 12 at thedesired location.

By way of clarification, the term “cannula” is used to denote cannula 14because it serves a primary purpose of transporting fluid into the bloodpump 12, whereas the term “catheter” is used to denote the catheter 132because it serves a primary purpose of guiding or directing devices orcomponents (i.e. the pump assembly 136) to a desired location within thebody. It is to be readily understood, however, that these terms are onlyused for convenience and in a general fashion such that the cannula 14may serve certain guiding functions and the catheter 132 may servecertain fluid transportation functions without departing from the scopeof the present invention. For example, the cannula 14 may be equippedwith dedicated lumens to receive various guide mechanisms (such as guidewires, balloon catheters, selectively deformable elements such asNitonol, etc). In similar fashion, the guide catheter 132 may be used totransport fluid to and/or from the patient, such as by providingapertures 138 along predetermined regions of the catheter 132.

FIG. 11 demonstrates a significant feature of the present inventioninvolving the use of the guide catheter 132 to transport fluid to and/orfrom the patient. An optional perfusion assembly 140 is provided as partof the intravascular blood pump system 130 of the present invention. Theperfusion assembly 140 includes a conduit 142 in fluid communicationwith the apertures 138, which in this case are formed near the distalregion of the guide catheter 132 a short distance downstream from theblood pump 12. In use, blood will pass along the exterior of the guidecatheter 132 for distribution throughout the body, as well as within theinterior of the guide catheter 132 after passing into the apertures 138.The perfusion assembly 140 may then be employed to selectively rerouteblood from within the guide catheter 132 to a point within the patient'svasculature downstream from the point where the guide catheter 132enters the body. A hemostasis valve assembly 146 of the perfusionassembly 140 permits the drive cable assembly 18 to pass through to thepurge fluid delivery system 26 while preventing blood flow other thaninto the perfusion assembly 140. A seal assembly 150 of the purge fluiddelivery system 26 permits the drive cable 62 to pass through to themotor 20 while preventing the flow of purge fluid other than into andfrom the purge fluid delivery system 26. The perfusion assembly 140includes a control mechanism 148 for selectively controlling thedistribution of perfusion blood flow from the perfusion assembly 140into the patient. This control mechanism 148 may be automatic based oncertain feedback criteria or manually operated.

FIGS. 12-17 illustrate an exemplary construction of the intravascularblood pump system 130 according to the third broad aspect of the presentinvention. As shown in FIG. 12, the conduit assembly 134 may beselectively disengaged so as to remove the pump assembly 136 therefrom.According to the present invention, the conduit assembly 134 may beintroduced (without the pump assembly 136) into the circulatory systemof a patient and selectively guided such that the rotor shroud 36 andcannula 14 are positioned at a desired location. The pump assembly 136can thereafter be selectively introduced into the conduit assembly 134.A challenge in such a “back-loading” arrangement is ensuring that thepump assembly 136 docks appropriately within the rotor shroud 36 and ismaintained in proper engagement during operation of the resulting pump12.

An exemplary docking arrangement will now be described with reference toFIG. 14. In a preferred embodiment, the rotor 44 may be properly andaccurately docked within the shroud 36 by forming angled mating surfaceson corresponding portions of the shroud 36 and pump body 34. Morespecifically, an angled mating surface may be formed on the interiorsurface of the rotor shroud 36 along that portion extending proximallyfrom the flow aperture 38. A corresponding angled mating surface may beprovided along the exterior surface of the pump body 34 along a distalportion thereof. The mating surfaces shown in FIG. 14 may preferably beformed in the range from about 2 degrees to 10 degrees, and morepreferably formed in the range from about 3 degrees to 6 degrees. Matingangles within these ranges are adequate to guide the distal end of thepump body 34 to a point generally flush with the proximal edge of theflow aperture 38 as shown in FIG. 14. In this fashion, the pump assembly136 and the rotor shroud 36 combine to form the blood pump 12. Moreimportantly, this docking is carried out such that the rotor 44 androtor blades 58 are maintained in proper position for efficient and safepump operation.

An exemplary biasing scheme for maintaining the pump assembly 136 inthis docked relationship will now be described with reference to FIGS.12-13 and 16-17. The conduit assembly 134 is preferably equipped with amale quick-connect coupling 152 capable of engaging with a femalequick-connect coupling 154 forming part of the perfusion assembly 140 ofthe present invention. A bias spring 156 is provided in between theperfusion assembly 140 and the housing 96 of the purge fluid deliverysystem 26. The bias spring 156 is preferably dimensioned so as to be intension when the male quick-connect 152 is engaged within the femalequick-connect 154 as part of the docking process of the presentinvention. As such, the bias spring 156 serves to maintain the pumpassembly 136 in the docked position within the rotor shroud 36. The biasspring 156 may be coupled to the housing 96 of the purge fluid deliverysystem 26 in any number of suitable fashions. One such couplingarrangement may comprise a female quick-connect coupling 158 attached tothe housing 96 and a male quick-connect coupling 160 attached to thebias spring 156.

An exemplary embodiment of the perfusion assembly 140 is shown withreference to FIGS. 12-13 and 17. The perfusion assembly 140 shownincludes the hemostasis valve 146 coupled to the female quick-connectcoupling 154. A length of tubing 162 extends between the opposing barbconnectors of the hemostasis valve 146 and the female quick-connectcoupling 154. A continuous lumen is formed extending through theinterior of the male quick-connect coupling 152, thefemale-quick-connect coupling 154, the tubing 162, and the hemostasisvalve 146. The drive cable assembly 18 extends through this continuouslumen and exits through a Touehy-Borst hemostasis seal 164 whichprevents the migration of blood out of the proximal end of the perfusionassembly 140. A side-port 166 is disposed in fluid communication withthe central lumen of the perfusion assembly 140. In one embodiment, thisside-port 166 may be equipped with a conduit 168 having a stop-cock 170to selectively control the distribution of blood through a perfusionconduit (i.e. conduit 142 of FIG. 11) coupled to the stop-cock 170. Itwill be appreciated that this type of manual control system forselectively perfusing the patient may be replaced with control circuitryfor automatically controlling the rate of perfusion. Such automaticperfusion may be based on control algorithms based on contemporaneousfeedback or pre-programmed thresholds.

The foregoing discussion details a host of inventive aspects formingpart of the present invention. It will be appreciated by those skilledin the art that changes could be made to the embodiments described abovewithout departing from the broad inventive concepts thereof. Thefollowing evidences, by way of example only, various additional aspectsforming part of the present invention.

FIG. 18 illustrates an alternate configuration of the intravascularblood pump system 130 of the third broad aspect of the present inventionhaving an alternate bearing assembly, purge fluid delivery, and dockingscheme. The bearing assembly includes a seal spring 182 and a bearingassembly 180. The bearing assembly 180 includes an inner race 184, anouter race 186, and a plurality of balls 188 which enable the inner race184 to rotate along with the rotor shaft 46 while the outer race 186remains in a static and fixed position relative to an inner surface ofthe pump body 34. An O-ring 190 is disposed within a groove formed inthe rotor shaft 46 so as to maintain the bearing assembly 180 againstthe seal spring 182. The O-ring 190 is further secured within the groovein the rotor shaft 46 via a contoured lip portion extending from thedistal end of the cable adapter 60. The proximal end of the cableadapter 60 flushly engages the drive cable 62.

The purge fluid delivery system of the embodiment shown in FIG. 18provides for a one way delivery of purge fluid to the blood pump 12.That is, pressurized fluid (namely, fluid pressurized to some levelelevated above the blood pressure in the surrounding vessel) is injectedin between the drive cable 62 and the interior of the protective sheath32 during operation. This serves to reduce any frictional heating thatexists between the drive cable 62 and sheath 32. The pressurized fluidalso flows through the interior of the pump 12 such that, if the seal at192 is broken, the pressurized fluid will flow past the open seal 192and onward through the blood flow ports 38 formed in the shroud 36. Thisserves to keep blood from entering the pump 12 in an effort to avoidclotting and/or damaging the pump 12.

The pump assembly 136 may be docked within the conduit assembly 134 inany number of different fashions without departing from the scope of thepresent invention. That is to say, the docking scheme shown in FIG. 18is set forth by way of example only and is not to be deemed limiting orrestrictive as to numerous ways to temporarily engage or “dock” the pumpassembly 136 within the conduit assembly 134. The only requirement isthat the pump assembly 136 and conduit assembly 134 dock such that therotor 44 is disposed within the shroud 36 to provide the desired axialflow through the cannula 14 and out the shroud 36. The exemplary dockingscheme involves forming an annular engagement groove 194 along theinterior of the shroud 36, and forming a complementary annular ridge 196along the exterior surface of the pump body 34. During insertion, thepump assembly 136 will be advanced into the conduit assembly 134 untilthe annular ridge 196 on the pump body 34 engages within the groove 194formed in the shroud 36. This docking scheme is generally advantageousin that the engagement action between the annular ridge 196 and groove194 will provide tactile feedback to the physician during the process ofinserting the pump assembly 136 into the conduit assembly 134 such thatthe physician will be able to determine when the docking has beencompleted.

As will be appreciated by those skilled in the art, the location of theannular ridge 196 and engagement groove 194 may be varied such that theyare disposed closer or farther away from the flow apertures 38. It maybe advantageous to form these docking structures close to the flowapertures 38 in an effort to thwart the ingress of blood into thejunction extending between the interior of the shroud 36 and theexterior surface of the pump body 34. It is also contemplated to employselectively inflatable structures, such as balloons, in an effort totemporarily engage or dock the pump assembly 136 within the conduitassembly 134. In this regard, one or more lumens may be formed withinthe pump body 34 extending from the interior of the pump body 34 influid communication with a balloon disposed along the exterior surfaceof the pump body 34. The pressurized fluid flowing within the interiorof the pump body 34 may then be used to inflate the balloon, which willthen engage within an annular groove in the shroud 36, such as at 194.Of course, the engagement structures may also be reversed withoutdeparting from the scope of the present invention. For example, theshroud 36 may be equipped with a fluid delivery lumen therein forinflating a balloon disposed on the interior surface of the shroud 36,which may in turn be disposed within an annular engagement groove formedalong the exterior surface of the pump body 34.

While this invention has been shown in use largely in during left-heartapplications it is to be readily appreciated that this does not limitthe applications of this invention for use in left heart support only.Rather, the guidable intravascular blood pump of the present inventioncan be utilized in right-heart support applications and a wide varietyof other applications apparent to those skilled in the art. For example,with reference to FIG. 19, shown is an intravascular blood pump 200 (ofthe type shown and described above with reference to FIGS. 2-5)configured for use in a right-heart support application. In thisembodiment, the intravascular blood pump system 200 is equipped, by wayof example, with an “over-the-wire” guide mechanism 16 comprising aballoon catheter 202. It is to be readily appreciated that, althoughshown and described below in terms of an embodiment of the type shown inFIGS. 2-5, the intravascular blood pump systems 120, 130 disclosedherein may also be configured for use in right-heart applications. Suchright-heart configurations, and others apparent to those skilled in theart based on the broad principles enumerated in this application, arecontemplated as being within the scope of the present invention.

The intravascular blood pump system 200 is shown positioned within theheart, such as may be advantageous to provide right heart support duringbeating heart surgery. To position the guidable intravascular blood pumpsystem 200 in the right heart according to the present invention, asuitable guide element (such as balloon catheter 202) is first advancedto a desired location within the heart via the “sail” action of aninflated balloon. After the balloon catheter 202 is located in thedesired position (such as in the pulmonary artery as shown), theintravascular blood pump system 200 according to the present inventionmay be advanced over the balloon catheter 202 and guided into a desiredarrangement. For right heart support, this would involve advanced intothe pump 12 and cannula 14 overt the balloon catheter 202 until thefluid inlet 204 is disposed within the vena cava (or right atrium) andthe fluid outlet 206 is positioned within the pulmonary artery. The pump12 may then be selectively (i.e. automatically or on-demand) controlledto transport blood from the vena cava (or right atrium) in atrans-valvular fashion through the tricuspid valve, the right ventricle,and the pulmonary valve for deposit within the pulmonary artery.Providing right-heart support during beating heart surgeryadvantageously overcomes conditions where cardiac output may becomecompromised during beating heart surgery, such as when the heart islifted to gain access to posterior vessels, thereby avoiding the needfor cardiopulmonary bypass.

It is also contemplated as part of the present invention that theguidable intravascular blood pump systems can be introduced into thepatient's vasculature to achieve the intravascular access into the rightor left heart through any number of access points, including but notlimited to the internal jugular vein, the brachiocephalic vein, carotidartery, axillary artery, femoral vein, femoral artery, and subclavianartery. The intravascular blood pump systems of the present inventionmay also be introduced via direct introduction, such as into the aorta,the atria, and the ventricles. As is well known in the art, suchintravascular access may be achieved percutaneously through the use ofthe Seldinger technique or directly through the use of minimallyinvasive access techniques.

Those skilled in the art will also appreciate that, although shown anddescribed above in terms of “axial flow,” the present invention is notlimited to the axial flow type intravascular blood pumps. Rather, theintravascular blood pumps 12 may comprise any number of suitable typesof intravascular blood pumps, including but not limited to so-called“mixed flow” intravascular blood pumps, without departing from the scopeof the present invention.

With regard to the embodiments shown in FIGS. 10-17, it is furthermorecontemplated that the guide catheter 132 may be separable from theconduit assembly 134 after the pump assembly 136 is docked within theshroud 36 to form the pump 12 at the desired location within thecirculatory system of the patient. This may be accomplished by providingthe guide catheter 132 in a detachable fashion via any number ofsuitable arrangements. By removing the guide catheter 132 after the pump12 assembled, wound management of the access point into the patient'svasculature may be improved. This is due, in part, to the substantialreduction in size of the device extending into the patient (i.e. thedrive cable assembly 18 as opposed to the larger diameter guide catheter132).

It is also contemplated to incorporate various pressure sensing and/orguidability features into at least one of the cannula, 14 and pump 12.Such features may include, but are not necessarily limited to, thoseshown and described in commonly-owned and co-pending U.S. patentapplication Ser. No. 09/280,988 (filed Mar. 30, 1999) entitled“Steerable Cannula,” and U.S. patent application Ser. No. 09/280,970(filed Mar. 30, 1999) entitled “Pressure Sensing Cannula,” thedisclosures of which are hereby expressly incorporated by reference asif set forth herein in their entirety and physically incorporated asAPPENDIX A and APPENDIX B respectively to the present specification.These pressure sensing features may include, but are not necessarilylimited to, the use of fluid-filled lumens, piezo-electric pressuresensing elements, strain gauges, and analysis of the torque/currentrelationship (based on the dynamic pressure differential between theinlet and outlet of the pump). The guidability features may include, butare not necessarily limited to, the use of side lumens and deformablematerials (i.e. Nitonol).

Various pump and cannula arrangements have been described and shownabove for providing right and/or left heart support wherein blood isdeliberately re-routed through and past the right and/or left ventriclein an effort to reduce the volume of blood to be pumped by theparticular ventricle. While “unloading” the ventricles in this fashionis preferred in certain instances, it is to be readily understood thatthe pump and cannula arrangements described herein may also be employedto “preload” the ventricles. Ventricular preloading may be accomplishedby positioning the outflow cannula from the pump into a given ventriclesuch that the pump may be employed to fill or preload the ventricle withblood. This may be particularly useful with the right ventricle. Onoccasion, the right ventricle is not supplied with sufficient levels ofblood from the right atrium such that, upon contraction, the rightventricle delivers an insufficient quantity of blood to the pulmonaryartery. This may result when the right ventricle and/or right atrium arein a stressed or distorted condition during surgery. Preloadingovercomes this problem by actively supplying blood into the rightventricle, thereby facilitating the delivery of blood into the pulmonaryartery. The same technique can be used to preload the left ventricle andthus facilitate the delivery of blood from the left ventricle into theaorta.

Appendix A—(U.S. Ser. No. 09/280,988) Steerable Cannula BACKGROUND OFTHE INVENTION

1. Field of the Invention

The invention relates to vascular cannulas for use in medicalprocedures.

2. Description of Related Art

In medical applications and specifically in surgery, the list of usesfor cannulas is exhaustive. Cannulas are to be distinguished fromcatheters in that catheters generally have a substantially smallerfluid-carrying capacity are used primarily for sampling or measurementpurposes or for delivery of small quantities of fluid, whereas cannulasare generally larger and are used for volumetric fluid transfer. Oneapplication of cannulas involves the augmenting or supplementing ofpulmonary blood flow through the beating heart during cardiac-surgery byuse of one or more cannulas involved in the intake and return of bloodinto the circulatory system. The cannulas interface between thepatient's circulatory system and the mechanical pumps that power theaugmentation procedure. Such an application is described in co-pendingPCT Application no. PCT/US97/18674 entitled “Single Port Cardiac SupportApparatus”, filed Oct. 14, 1997 and incorporated herein by reference inits entirety.

As will be appreciated, precise and quick placement of the cannula insurgical applications is critical, given the severe time constraintsfacing a surgeon whose patient's vital life sustaining functions havebeen suspended during the procedure. Currently, methods for placingcannulas in a patient's body are crude, in that they rely on guessworkand trial and error. Specifically, a surgeon will insert the cannula anddirect it towards the desired destination, but ultimately must feel byhand, through the patient's tissue for example, whether it has reachedthat destination. The surgeon may be forced to make several retractionsand re-insertions until the process succeeds. Shortcomings of such aprocedure are clear and may include damage to the delicate tissueinvolved and waste of valuable time. Additionally, constraints on theflexibility of the material are imposed since a prescribed amount ofrigidity is required to enable the cannula to be felt through the tissueand insure that the cannula does not collapse under insertion force.

Alternatively, the surgeon may rely on the use of guiding devices suchas a guide wire threaded through the cannula. The guide wire is ofteneasier to manipulate than the cannula, and its placement precedesplacement of the cannula. After the guide wire is in place, the cannulais pushed along the length of the guide wire, following the guide wireto the desired destination.

It is also known that a flow directed balloon catheter can be used as aguide wire. Balloon catheters are well known in the art and have amultitude of uses, including delivery or removal of fluid from thesurgical site. However, flow directed balloon catheters are typically atleast an order of magnitude smaller than cannulas. Their small sizeaccordingly severely limits their application since both quantity andrate of fluid flow through the catheter are limited. In fact it isprecisely because of their small size that flow directed ballooncatheters can be used as guiding devices for the larger, more robust andversatile cannulas. During use as a guiding device for a cannula, theflow directed balloon catheter acts as a guide wire in facilitating theadvancement of the cannula to the desired destination. The flow directedballoon catheter is first inserted into place in the patient's body, andthe cannula, threaded around the flow directed balloon catheter, is thenadvanced into the desired position.

Insertion of the flow directed balloon catheter is effected using theinflatable balloon disposed at a distal tip of the flow directed ballooncatheter. A lumen in communication with the balloon delivers inflatingfluid to the balloon, thereby inflating the balloon and causing it tooperate as a “sail” which is pulled along in the blood stream throughthe natural blood flow in the patient's circulatory system.

The above procedures have met with only limited success, and thereexists a long felt need for devices and methods that facilitateplacement of a cannula in a patient's body. A system that will assist inthe manipulation of the cannula through the vascular structure or otherbodily regions of the patient would accordingly serve to make theplacement process more efficient and less time-consuming, improving thechance of overall success of a surgical procedure.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the deficiencies of the prior art byproviding a cannula which can be steered during its advancement in thebody of the patient. Steering is implemented using cables connected to adeformable portion of the cannula. The cables extend to the proximal endof the cannula from where the operator can selectively apply tensionalforces to thereby cause the cannula to curve at the deformable portion.The deformable portion is disposed preferable at the distal end of thecannula, but may be located at other sites along the length of thecannula.

In accordance with a second embodiment of the invention, the cannula isprovided with more than one cable for facilitating deformation alongmultiple planes. Additionally, preformed curves may be provided alongthe length of the cannula, which curves can be either augmented orstraightened by applied tension to the cables.

The cannula, in accordance with a third embodiment, is provided with aspiraling wire formed in the cannula wall. The spiraling wire operatesto provide rigidity to the body of the cannula and maintain good fluidflow therein. The spiraling wire may comprise a portion of the cableused to impart deformation in an arrangement in accordance with a fourthembodiment of the invention.

In accordance with a fifth embodiment of the invention, the steerablecannula is provided with an inflatable balloon at the distal end thereoffor assisting in guiding the cannula to its desired destination. Theinflatable balloon is selectively inflatable using a lumen which effectsfluid communication between an fluid source and the balloon.

In accordance with a sixth embodiment of the invention, a steerablecannula having a pigtail distal tip configuration is provided.

In accordance with a seventh embodiment of the invention, a steerablecannula having a movably supported guide wire is provided.

In accordance with an eighth embodiment of the invention, a steerablecannula having an integrally formed guide wire is provided.

In accordance with a ninth embodiment of the invention, a steerablecannula is used in a co-axial cannula arrangement.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 20 is schematic side view of a steerable cannula in the undeformedstate in accordance with the first embodiment of the invention;

FIG. 21 is a schematic cross-sectional view of the steerable cannula ofFIG. 20 taken along line A-A;

FIG. 22 is a schematic side view of the steerable cannula in thedeformed state in accordance with the first embodiment;

FIG. 23 is a schematic cross-sectional view of a steerable cannulahaving two cables in accordance with a second embodiment of theinvention;

FIG. 24 is a schematic side view of a steerable cannula having areinforcing wire in accordance with a third embodiment of the invention;

FIG. 25 is a schematic cut-away view of a steerable cannula inaccordance with a fourth embodiment of the invention;

FIG. 26 is a schematic cross-sectional view taken along line B-B of FIG.25;

FIG. 27 is a schematic side view of a steerable cannula having apreformed curve and an inflatable balloon formed at a distal end thereofin accordance with a fifth embodiment of the invention;

FIG. 28 is a schematic side view of the inflatable balloon of fifthembodiment of the invention, wherein the balloon is shown in theinflated state;

FIG. 29 is a schematic cross-sectional view taken along line C-C of FIG.28;

FIG. 30 is a schematic view showing a steerable cannula having a pigtaildistal tip configuration in accordance with a sixth embodiment of theinvention;

FIG. 31 is a schematic view showing a steerable cannula having aguidewire distal tip configuration in accordance with a seventhembodiment of the invention;

FIG. 32 is a schematic view showing a steerable cannula having aguidewire distal tip configuration in accordance with an eighthembodiment of the invention;

FIG. 33 is a schematic side view showing a steerable cannula used in aco-axial configuration in accordance with a ninth embodiment of theinvention, wherein the steerable cannula is advanced to a first relativeposition;

FIG. 34 is a schematic side view showing a steerable cannula of FIG. 33,wherein the steerable cannula is advanced to a second relative position;and

FIG. 35 is a schematic side view of a configuration in accordance with atenth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a steerable cannula in which a portionwhich is adapted for insertion into the body of a patient, preferablyinto the vascular system of the patient, is configured to be selectivelydeformable. The deformation aids in changing the direction of thecannula during the insertion process such that the cannula can besteered in a desired direction as it is advanced toward its destinationin the patient's body. Deformation is effected using a cable connectedwith the deformable portion of the cannula. Tension on the cable,induced by for example rotating a portion of a handle disposed at aproximal end of the cannula exterior of the body of the patient, resultsin tension on one wall of the deformable portion and thereby causes itto bend in the direction of the cable.

With reference to FIGS. 20-23 in which an exemplary arrangement inaccordance with a first embodiment of the invention is shown, cannula1120 can be seen as comprising a substantially cylindrical structurehaving a wall 1122 which defines a main lumen 1124. Lumen 1124 isadapted for fluid transport to or from the body of the patient and maybe provided with one or more holes 1126 located adjacent to distal tip1128 and permitting passage of fluid therethrough. Holes 1126 supplementfluid flow through main port 1125, especially in situations of blockageof main port 1125. Cannula 1120 may be one of two complementary cannulas(not shown) used in a surgical procedure, one for intake and the otherfor removal of blood or other fluid from the patient's body.Alternatively cannula 1120 may comprise a component of a co-axial,single port device in which cannula 1120 is surrounded by a second,larger conduit, with cannula 1120 for example operating to intake bloodfrom the patient towards a pump system and the conduit operating toreplace the blood from the pump back into the patient for augmentationof blood flow during beating heart surgery as described in co-pendingPCT Application no. PCT/US97/18674 mentioned above.

At a proximal end 1130 of cannula 1120 is provided a handle 1132 whichserves to transmit turning forces applied by an operator's hand to thecannula to aid in its manipulation in the patient's body. As such,handle 1132 is rigidly attached to wall 1122 of cannula 1120, althoughportions of handle 1132 may be configured for motion relative to cannula1120 in order to impart the necessary tension on cables used fordeforming the cannula 1120 as described below. Rotation of the rigidlyattached portion of handle 1132, results in a corresponding rotation ofthe distal end 1128 of the cannula 1120 within the patient's body, thusaiding in the cannula's manipulation and advancement to the desireddestination.

Wall 1122, in addition to defining main lumen 1124 of cannula 1120,contains a secondary lumen 1136 formed therein. Movably mounted in lumen1136 is a cable 1138 which is secured at point 1140 in wall 1122. Point1140 may be disposed anywhere along the length of the cannula 1120, butin the preferred embodiment lies at distal end 1128.

Cannula 1120 is provided with a deformable portion 1142 formed along atleast a segment of its length. In the exemplary arrangement shown inFIGS. 20-22, deformable portion 1142 is disposed in close proximity todistal end 1128 of cannula 1120; however, it is to be understood thatthis not intended to be limiting and that other regions in the cannula1120 can alternatively or additionally be made deformable depending onthe contemplated application.

Deformable portion 1142 serves to cause cannula 1120 to bend in responseto tension applied to cable 1138 and thereby assume a configuration asshown in FIG. 22. Depending on the location of point 1140 and thelocation of lumen 1136 radially and axially along wall 1122, appliedtension to cable 1138 causes cannula 1120 to turn on itself in thedirection of pull to thereby assume a curve having a predeterminedorientation. Additionally, if cannula 1120 is provided with one or morepreformed curves, which may be in identical or in different planes alongthe length of the cannula as is contemplated, tension in cable 1138 canoperate to temporarily straighten the cannula along at least one ofthese planes to facilitate handling during a particular maneuver throughthe patient's body.

It is also contemplated that more than one cable can be provided,supported in suitable secondary lumens formed in cannula 1120. As can beseen from FIG. 23, a second lumen 1146 can be provided in wall 1122 ofcannula 1120, second lumen 1146 movably supporting cable 1144 therein.Cables 1138 and 1144 are thus disposed on opposite sides of cannula 1120and serve to provide steerability in two directions. The cables areconfigured such that a pulling of one cable is coordinated with aslacking of the other cable in order permit bending of cannula 1120 atdeformable portion 1142. Although shown to be diametrically opposed inposition, cables 1138 and 1144 can occupy any position along wall 1122,and it will be appreciated that the number of such cables used can varydepending on the application, as can their distribution in wall 1122,and any desired number of turning directions can accordingly be achievedin accordance with the present invention.

Wall 1122 can be formed of materials ranging from rigid to flexible, andin the preferred embodiment comprises a semi-rigid transparent materialsuch as silicone rubber. Of course it is to be understood that bydefinition deformable portion 1142 is to be constructed of a flexiblematerial, regardless of the construction of the remainder of the wall1122, such that cannula 1120 can bend when appropriate pulling forcesare imparted through the cable(s).

Selective bending of cannula 1120 can also be facilitated using a coremember provided for this purpose. Core member 1182, preferable formed ofmaterial having appreciable stiffness relative to wall 1122, is disposedlongitudinally within cannula 1120 and serves to provide a deflectionpoint to locate and control the bending point of the cannula. Core 1182is removable and can be movable distally or proximally within cannula1120 in order to alter the deflection point. In this manner also flowblockage in the cannula 1120 can be insured during insertion.

As can be seen from FIG. 24, a spiraling wire 1148 can be provided forstructural reinforcement of cannula 1120. Wire 1148 is either moldedinto the wall 1122 or is otherwise supported therein, and extends eitherpartially or fully across the length of the cannula 1120. Wire 1148facilitates handling of the cannula 1120 and reduces the possibility ofcannula 1120 collapsing or being pinched shut and thus closing off theflow of fluid to or from the patient. Other ways of reinforcing thetubular body of cannula 1120 are known in the art and will adapt equallywell to the present invention. In addition, no reinforcement may beneeded if the cannula material is sufficiently rigid or if sufficientfluid flow is present within the cannula.

Alternatively, as shown in FIGS. 25-26, spiraling wire 1148 can itselfcomprise a portion of cable 1138. In such an arrangement, cannula wall1122 is formed of two layers 1162 and 1164, between which is formed alumen 1166. Layers 1162 and 1164 may be discrete layers bonded togetherat appropriate regions, or they may be a single layer folded back uponitself to form the two layers, with lumen 1166 and wire 1148 occupyingpredetermined regions therebetween. Cable 1138 is housed in a polymidetube 1170 disposed in lumen 1166 and extends beyond the end 1168 of tube1170 to then spiral exteriorly of inner layer 1162 and interiorly ofouter layer 1164 to thereby lend structural support to the cannula 1120.Metal or other tape 1172 can be used to secure spiraling wire 1148 inplace. In a variation of this, cable 1138 and wire 1148 may be twodiscrete components which are welded or otherwise connected together atany desired point along the body of cannula 1120. Alternatively, asshown in FIG. 35, cable 1138 may be secured to a band 1184 disposedradially about or adjacently to tip 1186 of cannula 1120. In all ofthese variations, cable 1138 may be formed of single or multiple strandsof metal, plastic or carbon fiber composite, but preferably cable 1138is formed of a single strand of stainless steel having a TEFLON™coating. In the FIGS. 33-35 arrangements, cannula 1120 is shown with anatraumatic bullet tip 1186 having side holes 1188 and end holes 1190. Itwill be appreciated that such a tip can be provided for any arrangementof the invention. It will also be appreciated that the tip 1186 canitself serve as the anchor for the cable 1138 in certain arrangements.The tip 1186 is fixedly bonded to distal end 1125 of cannula 1120 andenables a simplified construction of the steering mechanism and providesa blunt surface that will not injure tissue in the body.

Lumens 1136 and 1146, or other similar lumens, in addition to supportingcables 1138 and 1144 therein, may be used to supply inflating fluid to aballoon 1150 provided at the outer surface of the distal end 1128 ofcannula 1120. As shown in the exemplary embodiment of FIGS. 27-29,balloon 1150 is in fluid communication with inflating fluid source 1152,via supply tube 1154 and lumen 1156. Fluid source 1152 serves toselectively provide fluid, such as saline, air or other gas, to balloon1150 to thereby cause the balloon to inflate within the patient's body.Balloon inflation in this manner assists in placement of the cannula1120, especially when inserting the cannula antegrade, with the inflatedballoon serving to float the tip of cannula within the fluid flow tothus transport it to the desired location in the body. Cannula 1120 isprovided with one preformed curve 1158 in addition to curve 1160imparted by the tension in cable 1138. Balloon 1150 is shown in thedeflated state in FIG. 27 and in the inflated state in FIGS. 28 and 29.

Various distal tip configurations can be selected for cannula 1120,depending on the particular application as appreciated by those ofordinary skill in the art. For example, a pigtail shape can be used forcrossing the aortic valve retrograde. The pigtail shape, illustrated inFIG. 30, can be formed by bonding or thermal welding or otherwiseattaching a thermoplastic rod 1174 formed into a loop at the distal endof the cannula 1120. Alternatively, a J-tip wire 1176 can be configuredto protrude from the distal tip 1128, as illustrated in FIGS. 31 and 32.The J-tip wire can be a conventional guidewire movable or fixedlysupported in a dedicated lumen 1178 formed in a rigidly attached tube1180 (FIG. 31), or it can be supported, rigidly or movably, betweenlayers of material from which the wall 1122 of cannula 1120 is formed.Guidewires are known in the art and can for example be formed ofwindings of wire coiled around a core and having one or more preformedcurves formed therein.

An embodiment in which cannula 1120 is used in a coaxial configurationis shown in FIGS. 33 and 34. Cannula 1120 serves as an inner cannula,passing through outer conduit 1180 while the two components are disposedin the patient's body. An important advantage of this arrangement isthat outer conduit 1180 operates to vary the radius of curvature ofinner cannula 1120 by providing a base point as the inner cannula 1120is advanced. In this manner manipulation of the inner cannula 1120 andouter conduit 1180 is facilitated and advancement to the desireddestination in the body of the patient is more efficiently accomplished.

The above are exemplary modes of carrying out the invention and are notintended to be limiting. It will be apparent to one of ordinary skill inthe art that modifications thereto can be made without inventivedeparture from the spirit and scope of the invention.

Abstract of U.S. Ser. No. 09/280,988

A steerable cannula is provided with at least one cable through whichtension is communicated to a deformable portion of the cannula. Thetension causes the cannula to bend at the deformable portion, enablingselective steering of the cannula during insertion into the body of thepatient.

Appendix B—(U.S. Ser. No. 09/280,970) Pressure Sensing CannulaBACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to cannulas used in surgical applications,and more particularly, to a cannula equipped with a pressure/flow ratetransducer.

Description of the Related Art

In medical applications and specifically in surgery, the list of usesfor cannulas is exhaustive. One application involves the augmenting orsupplementing of pulmonary blood flow through the beating heart duringcardio-surgery by use of one or more cannulas involved in the intake andreturn of blood into the circulatory system. The cannulas interfacebetween the patient's circulatory system and the mechanical pumps thatpower the augmentation procedure. Such an application is described inco-pending PCT Application no. PCT/US97/18674 entitled “Single PortCardiac Support Apparatus”, filed Oct. 14, 1997 and incorporated hereinby reference in its entirety.

When performing cardiac surgery cannulas are placed within the patient'sblood stream and used for inflow and outflow of blood or other fluids.If the operator wishes to determine the rate of fluid flow, either acatheter with appropriate sensors must also be placed in the patient'sblood stream, or other sensors such as an external ultrasonic sensor asdisclosed in U.S. Pat. No. 5,179,862 are used. A shortcoming ofultrasonic systems such as that described in U.S. Pat. No. 5,179,862 isthat they require significant monitoring. Ultrasonic sensors alsorequire that tubing of a specific diameter be used, thereby adding tothe cost and complexity of the surgical procedure. Additionally,ultrasonic sensors are expensive and nondisposable, thereby adding tothe cost of the surgical procedure.

Another method to measure flow rate is through the use of athermodilution catheter. Thermodilution catheters require the infusionof a solution, typically saline, of a known temperature, with a distallydisposed thermistor measuring the temperature change to determine theflow rate. This method is also expensive, increasing the cost of thesurgical procedure. A second problem with using flow-sensing catheters,such as thermodilution catheters, is that they require the operator toplace more incisions within the patient. The catheters must be placed sothat they do not interfere with the inflow or out flow of the cannula.Visual markers along the length of the cannula may also be used todetermine location, the greater the number of markers the more accuratethe placement at the expense of quick readings due to the greater numberof markings.

SUMMARY OF THE INVENTION

The present invention overcomes the deficiencies of the prior art byproviding a cannula assembly having one or more pressure transducerscoupled to a main lumen thereof. In accordance with a first embodiment,the pressure transducers are attached to the substantially tubular walldefining the main lumen.

In accordance with a second embodiment, a partial occlusion is providedin the cannula to increase the pressure drop across the main lumen. Inthis manner transducer signal is increased, and an improved differentialpressure measurement signal achieved.

In accordance with a third embodiment of the invention, one or morepressure transducers are used in conjunction with a pair of coaxialcannulas for measuring pressure.

In accordance with at fourth embodiment of the invention, a differentialpressure transducer is used, the differential pressure transducer beingmounted in a dedicated secondary lumen in communication with the firstlumen.

In accordance with a fifth embodiment of the invention, the secondarylumen housing the differential pressure transducer is disposed across aknee formed in the cannula to augment pressure measurement. Partialocclusions may also be provided for this purpose.

In accordance with a sixth embodiment of the invention, the secondarylumen housing the differential pressure transducer is formed integrallywith the tubular wall defining the main lumen.

In accordance with a seventh embodiment of the invention, a soft,flexible tapered tip is provided at the distal end of the cannula. Sucha configuration allows for easier negotiation through the patient's bodyduring surgical procedure.

In accordance with an eighth embodiment of the invention, an inflatableballoon is provided at the distal end of the cannula. The inflatableballoon aids in transporting the cannula to the desired destination.

In accordance with a ninth embodiment of the invention, a guide wirelumen is provided for supporting a guide wire in the cannula. The guidewire is used as a predecessor step in the insertion of the cannula.

In accordance with a tenth embodiment of the invention, a light guide issupported in the cannula. The light guide conveys light to apredetermined portion of the cannula to thereby aid in the visualizationand location of the cannula during the surgical procedure.

The invention realizes various advantages over the prior art, includinga reduction in the number of incisions that a surgeon must make inperforming surgical procedures, along with a reduction in the amount offoreign material introduced into the patient's body, while providingsafe, rapid, accurate and cost-effective fluid flow rate measurements.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 36 is a schematic side view of a first embodiment of the invention;

FIG. 37 is a schematic cross-sectional view taken along line D-D of FIG.36;

FIG. 38 is a schematic cross-sectional view taken along line E-E of FIG.36;

FIG. 39 is a schematic view of a cannula in accordance with theinvention in a surgical application;

FIG. 40 is a schematic partial cut-away side view of a second embodimentof the invention;

FIG. 41 is a schematic cross-sectional view taken along line F-F of FIG.40;

FIG. 42 is a schematic side view of a third embodiment of the invention;

FIG. 43 is a schematic side view of a fourth embodiment of theinvention;

FIG. 44 is a schematic side view of a fifth embodiment of the invention;

FIG. 45 is a schematic side view of a sixth embodiment of the invention;

FIG. 46 is a schematic cross sectional view taken along line G-G of FIG.45;

FIG. 47 is a schematic side view of a seventh embodiment of theinvention;

FIGS. 48 and 49 are schematic side views of an eighth embodiment of theinvention;

FIG. 50 is a schematic cross-sectional view taken along line H-H of FIG.49;

FIG. 51 is a schematic side view of a ninth embodiment of the invention;

FIG. 52 is a schematic side view of a tenth embodiment of the invention;and

FIG. 53 is a schematic cross-sectional view taken along line K-K of FIG.52; and

FIG. 54 is a schematic side view of an eleventh embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the invention, a cannula comprising a substantiallytubular, semi-flexible material adapted for fluid transport whileinserted in a patient's body is provided with one or more pressuretransducers which are fixedly or adjustably supported in the cannula.The pressure transducers are disposed internally or externally of thecannula and are used to provide a measurement of the rate of fluid flow.In the internal configuration, the rate of fluid flow within the cannulais measured. In the external configuration, the rate of fluid flowoutside the cannula is measured. The cannula can also be adapted tosupport a guide wire to aid the operator in its insertion through thepatient's body, and/or a light source to provide a visual referenceduring the insertion procedure. It is to be understood that the use ofthe term “cannula” is intended to encompass cannulas, catheters, and anyrelated devices having similar application.

An exemplary arrangement in accordance with a first embodiment of theinvention is shown FIGS. 36-38. Cannula 2220 comprises a substantiallycylindrical structure having a wall 2228 defining a main lumen 2221.Wall 2228 can be formed of materials ranging from rigid to flexible, andin the preferred embodiment comprises a semi-rigid transparent materialsuch as polyurethane, silicone rubber or other material. Lumens otherthan main lumen 2221 may also be provided, as described below. Thecannula may also be formed from vinyl plastisol. To form a cannula ofvinyl plastisol, a mandrel is dipped into liquid vinyl plastisol andheated. Wire is then wrapped around the mandrel and first formed layer.The mandrel is then dipped again encasing the wire, and then heated. Themandrel is then removed. Lumens and transducers may be formed within thewall of the cannula during the dipping process.

To lend structural support for the thin wall which allows maximum flowwith minimal insertion damage, spiraling wire 2230 is provided forreinforcement and is either molded into the wall 2228 or is otherwisesupported therein, and extends either partially or fully across thelength of the cannula 2220. Wire 2230 facilitates handling of thecannula 2220 and reduces the possibility of cannula 2220 collapsing orbeing pinched shut and thus closing off the flow of fluid to or from thepatient. Other ways of reinforcing the tubular body of cannula 2220 areknown in the art and will adapt equally well to the present invention.In addition, no reinforcement may be needed if the cannula material issufficiently rigid or if sufficient fluid flow is present within thecannula.

A connector 2223 is provided at the proximal 2225 end of cannula 2220.Connector 2223 is suitably sized to interface with various surgicalinstruments, including but not limited to a reverse flow pump or fluidconduits leading thereto (not shown). Cannula 2220 may also have one ormore holes 2226 located adjacent to distal tip 2222 to facilitate fluidflow therethrough. Cannula 2220 may be one of two complementary cannulasused in a surgical procedure, one for intake and the other for removalof blood or other biocompatible fluid from the patient's body.Alternatively, cannula 2220 may comprise a component of a co-axial,single port device in which cannula 2220 is surrounded by a second,larger conduit, with cannula 2220 for example operating to intake bloodfrom the patient towards a pump system and the conduit operating toreplace the blood from the pump system back into the patient foraugmentation of blood flow during beating heart surgery as described inthe co-pending PCT Application No. PCT/US97/18674 mentioned above.

In order to provide real time fluid flow information in accordance withthe present invention, a pair of pressure transducers 2224, 2232 areprovided at two separate locations as illustrated in FIG. 36. Pressuretransducers 2224, 2232 are of the type known in the art and eachcomprises for instance a piezo-electric crystal housed in an integratedcircuit (IC) chip (not shown). The crystal configuration is designed tobe pressure sensitive, generating an electrical signal in proportion tothe amount of pressure experienced.

The principle governing the relationship between fluid flow and pressureis defined by Bernoulli's equation, herein solved for flow rate V and isdetermined by:

$V = \sqrt{\frac{\Delta\;{P \cdot 2}\;{d \cdot a^{2}}}{f \cdot L \cdot \rho}}$where ΔP is the measured difference in pressure, d is the internaldiameter of the lumen, a is the area of the lumen, f is a frictionalfactor of the lumen material, L is the lumen length over which thepressure measurement is conducted, and ρ is a measurable constantrepresentative of the density of the fluid. The flow rate informationcan be used for a variety of purposes, including monitoring thepatient's condition and controlling the fluid pump used during theprocedure.

In the preferred embodiment, transducers 2224, 2232 are imbedded in thewall 2228, which is formed for instance by application of successivelayers of laminate and interjecting the transducers therebetween duringthe layering process. Depending on at what stage in the layering processthe transducers 2224, 2232 are put in place in the wall 2228, theirproximity to the interior of the cannula 2220 or its exterior can becontrolled in order to optimize measurement of cannula interior orexterior pressure. From the interior pressure measurements, adetermination of flow rate within main lumen 2221 can be made using theknown diameter of the main lumen 2221. Similarly, from the exteriorpressure measurements, flow rate of exterior fluid—for example,blood—can be measured if the diameter of the blood channel, such as theartery, is known, or the cannula can be calibrated with thermodilutioncatheters which assume the diameter of the vessel or artery they areplaced within.

In the FIG. 36 exemplary arrangement, pressure transducer 2232 isdisposed at a location near the distal tip 2222 of cannula 2220, whilepressure transducer 2224 may be disposed anywhere along the length ofcannula 2220 between pressure transducer 2232 and proximal end 2225. Itis also contemplated that the pressure transducers 2224, 2232 may bedetachably disposed in dedicated secondary lumens formed in or alongtubular wall 2228, the dedicated secondary lumen extending to theproximal end 2225 and supporting any electrical cables connected to thepressure transducers 2224, 2232. In the detachable arrangement, thelocation of pressure transducers 2224, 2232 in the cannula 2220 can beadjusted to suit the particular application, such that one transducercan be disposed within one chamber of the heart while the other is at adifferent of portion of the heart to thereby provide a pressure/flowrate measurement of a predetermined portion of the patient's body, forexample flow into the heart from a designated blood vessel. Such anapplication is shown in FIG. 39.

Pressure transducers 2224, 2232 are in electrical communication withconsole 2236 via cable 2238, which is supported in secondary lumen 2242provided in cannula 2220. Calculations for determining fluid flow rateusing signals generated by the pressure transducers 2224, 2232 andrelayed via cable 2238 are conducted at the console 2236 or at anyprocessor or processing system connected thereto.

As shown in FIGS. 40 and 41, cannula 2220 may also contain a partialocclusion portion 2247 that forms a venturi 2246 within the main lumen2221 of cannula 2220. Venturi 2246, which may be disposed anywhere alongthe length of the cannula 2220, induces a pronounced pressure drop,creating a greater differential in pressure between proximal region 2225and distal region 2222, thereby requiring less signal amplification ofthe pressure transducers and less filtering of the signal andconsequently yielding a more accurate flow rate measurement. Preferablythe location of the pressure transducer 2232 is in the vicinity ofventuri 2246 as shown in FIG. 54.

FIG. 42 shows an embodiment in accordance with the invention in whichthe pressure transducers 2224, 2232 are used with a co-axial, singleport device 2250 in which cannula 2220 is surrounded by a second, largerconduit 2248, with cannula 2220 for example operating to intake bloodfrom the patient towards a pump system (not shown) and conduit 2248operating to replace the blood from the pump system, via openings 2252,back into the patient for augmentation of blood flow during beatingheart surgery as described in the co-pending PCT Application no.PCT/US97/18674 mentioned above. It is to be understood that pressuretransducers 2224, 2232 can be mounted fixedly or detachably either tothe interior or exterior of either the cannula 2220 or the conduit 2248in the above-described manner. More than one pair of these transducerscan also be used in a myriad possible combinations in accordance withthe invention. In the preferred embodiment, the cannula 2220 is providedwith a bullet nosed tip, as illustrated in for example FIGS. 42-44.Other tip configurations, such as a bevel, may also be used, as will beappreciated by those skilled in the art.

An alternative to using pairs of pressure transducers such astransducers 2224, 2232 is the use of a single differential pressuretransducer 2254, as shown in FIG. 43. Differential pressure transducersare also well known in the art and comprise for example a piezo-electriccrystal electro-mechanically configured to be responsive to a pressuredifference between two opposing sides thereof. These two sidescorrespond respectively to proximal end 2257 and distal end 2259 ofsecondary lumen 2256 in which transducer 2254 is mounted. Proximal anddistal ends 2257 and 2259 are attached at any desired points along thelength of cannula 2220 to thereby couple secondary lumen 2256 to mainlumen 2221 and provide a pressure difference measurement between thedesired points. Attachment of lumen 2257 and transducer 2254 across knee2249 of cannula 2220, as shown in FIG. 44, will provide a strongersignal, with knee 2249 operating in accordance with the same principalas venturi 2246 discussed above. Thus it is to be understood that aventuri could also be used in conjunction with the differential pressuretransducer 2254. The ports 2261 and 2263 at which the lumen 2256interfaces with cannula 2220 may be sealed by an appropriate membrane,with saline or other fluid being permanently housed in the lumen 2256.Alternatively, ports 2261 and 2263 may be open, permitting fluidcommunication between the cannula 2220 and the lumen 2256 and attachedtransducer 2254. The latter, open configuration would achieve a morefaithful pressure representation. Stopcocks 2274 and 2276 can beprovided in the ports 2261 and 2263 to permit priming and/or de-airingof the ports. It should also be noted that although in the arrangementsof FIGS. 43 and 44 the lumen 2256 is provided as a separate tubularstructure, lumen 2256 may alternatively be formed integrally with wall2228 of cannula 2220, again with ports 2261 and 2263 being either openor closed to main lumen 2221 depending on the application. Such anarrangement is illustrated in FIGS. 45 and 46 in which is showntransducer 2254 in communication with lumen 2272 integrally formed inwall 2228 of cannula 2220.

Various distal tip configurations can be selected for cannula 2220 andused with the pressure sensing transducers, depending on the particularapplication as appreciated by those of ordinary skill in the art. FIG.47 shows an exemplary embodiment in which the distal tip 2222 is formedof a soft, flexible material having a bullet shape. As shown exemplarilyin FIGS. 48-50, the cannula 2220 may be equipped to support other tools,such as an inflatable balloon 2240 which is deployed for example inorder to assist in transporting the distal tip 2222 to the desireddestination in the patient's body during the surgical procedure. Balloon2240 is inflated through an inflating lumen 2244 provided in cannula2220 using a bio-compatible fluid such as saline or carbon dioxide gas.Preferably inflating lumen 2244 is formed integrally within wall 2228,by leaving an appropriate gap during the fabrication process, and isprovided with a fitting (not shown) at its proximal end to interfacewith an inflating device for supplying the bio-compatible fluid. Thelumen 2221 within the cannula 2220 can also be adapted to support aballoon catheter (not shown) which can be used to place the cannulawithin the patient's body. An obturator (not shown) may also be disposedthrough the main lumen 2221 to aid in insertion and guiding within thepatient's body.

Another tool which cannula 2220 may support is shown in FIG. 51 andcomprises a J-hook guidewire 2262 disposed slideably within lumen 2264,which is formed integrally in wall 2228 of cannula 2220. In operation,guidewire 2262, easier to manipulate than the cannula 2220, is firstinserted into the patient's body and manipulated to the surgical site.Subsequently the cannula 2220 is maneuvering along the guidewire 2262,which passes through lumen 2264, to the desired destination.

As illustrated in FIGS. 52 and 53, cannula 2220 may also contain a lightguide 2266, which may be supported in lumen 2268. Light guide 2266comprises one or more optical fibers formed of, for example, glass orother materials, such as plastic, known for that purpose. Distal tip oflight guide 2266 is configured for light projection, such that lightprovided at the proximal end of light guide 2266 is projected therefrom.An appropriate shape for such projection is a spherical shape, althoughother shapes and projection schemes, such as directional projection,fall within the purview of the invention. The source of light may be anyconventional monochromatic (laser/LED) or polychromatic device 2270, andmore than one light source with associated light guide can be used forcolor coding and providing a visual reference to different portions ofthe cannula 2220, depending on the colors of light used and on thelocation of the projection terminus of the light guides. In this mannercannula 2220 can be visually guided through the patient's body, relyingon the transmissivity of tissue to permit the location of theilluminated cannula in the patient's body. As will be appreciated, thelocation of the cannula 2220 can also be determined by examining thepressure waveform detected by the pressure transducers 2224, 2232 and2254. The physiological pressure waveform recorded by the transducerscan be used to determine the location of cannula 2220 in relation to thevalves of the patient's heart.

As will be appreciated by those skilled in the art, cannula 2220 may beprovided with one or more preformed curves along its length to aid inits manipulation through the patient's vasculature. Multiple curves maybe disposed along the same plane or in different planes, depending onthe application.

An additional feature in accordance with the invention is the use ofradiopaque markings (not shown) anywhere along the cannula body. Suchmarkings render portions of the cannula 2220 visible to x-ray radiationfor visualizing the cannula during its use.

The above are exemplary modes of carrying out the invention and are notintended to be limiting. It will be apparent to those skilled in the artthat modifications thereto can be made without departure from the spiritand scope of the invention. It will also be apparent that all devicesand methods herein disclosed will adapt equally to animal use as well ashuman use.

What is claimed is:
 1. A method for providing left-heart support usingan intravascular blood pump system, wherein the intravascular blood pumpsystem comprises: an intravascular blood pump adapted to be guided to apredetermined location within the circulatory system of a patient by aguide wire and configured to provide left-heart support, theintravascular blood pump comprising a rotor having a rotor hub taperingin the distal direction, at least one blade extending radially outwardfrom the rotor hub, the rotor hub having a distal end extending distallybeyond a most distal portion of the at least one blade; a cathetercoupled to a proximal end of the intravascular blood pump, a purge lumenextending through the catheter; a cannula coupled to a distal end of theintravascular blood pump, one or more first ports and one or more secondports establishing fluid communication between a cannula lumen and anexterior region of the cannula, wherein at least one first port islocated in proximity to the rotor and at least one second port is spacedapart from and located distal to the at least one first port; and anelongate lumen associated with the cannula and sized to slidably receivethe guide wire and dimensioned such that the guide wire passes slidablyand coaxially through the elongate lumen, the elongate lumen is sizedsmaller cross sectionally than the cannula lumen, both the elongatelumen and the cannula lumen not extending through the rotor hub; whereinthe method for providing left-heart support comprises the steps ofpassing the guide wire into the patient such that a distal end of theguide wire is positioned in the left ventricle of the patient's heart;placing the guide wire through both the cannula and the elongate lumensuch that the guide wire extends proximally away from the intravascularblood pump, the guide wire not passing through the rotor hub or thecatheter, and the guide wire extends out of the intravascular blood pumpsystem in a distal direction through the elongate lumen; advancing thecannula into the patient using the guide wire and positioning thecannula across an aortic valve of the patient such that a distal end ofthe cannula and the at least one second port are positioned in the leftventricle and a proximal end of the cannula and the at least one firstport are positioned in the aorta; passing purge fluid through the purgelumen to the intravascular blood pump; measuring pressure adjacent theintravascular blood pump; and spinning the rotor so as to pump bloodfrom the patient's heart into the at least one second port through thecannula lumen and out the at least one first port to provide left-heartsupport.
 2. The method of claim 1 wherein the guide wire enters theintravascular blood pump system through one end of the elongate lumenand exits the intravascular blood pump system through an opposite end ofthe elongate lumen.
 3. The method of claim 1 wherein the cannula ispositioned such that the elongate lumen lies wholly within the leftventricle during left-heart support and the elongate lumen is distal tothe intravascular blood pump.
 4. The method of claim 1 wherein the guidewire and intravascular blood pump system are inserted into and advancedalong the femoral artery towards the patient's heart.
 5. The method ofclaim 1 further comprising the step of pressurizing the purge fluid to apressure sufficient to avoid clotting of the patient's blood andsufficient to assure that the pressure is higher than the patient'sblood pressure adjacent the intravascular blood pump.
 6. The method ofclaim 1 further comprising the step of increasing blood volume in theleft ventricle to facilitate pumping of blood out of the left ventricle.7. The method of claim 1 further comprising the step of inserting aguide catheter into the patient, wherein the guide wire is placed in thepatient through the guide catheter.
 8. The method of claim 1 furthercomprising the step of calculating blood pressure adjacent theintravascular blood pump.
 9. The method of claim 1 further comprisingthe step of removing the guide wire from the patient after the cannulais advanced into the patient.
 10. The method of claim 1 wherein theintravascular blood pump system further comprising a housing connectedto a proximal end of the catheter and first and second conduits eachconnected to the housing, at least one of the first conduit and secondconduit in fluid communication with the purge lumen, the housing remainsoutside the patient while providing left-heart support; and wherein themethod further comprising the step of pumping the purge fluid throughone of the first and second conduits, through the housing and purgelumen to the intravascular blood pump.
 11. The method of claim 1 whereinthe cannula is reinforced with a spiral wire and wherein the purge lumenis a side lumen extending longitudinally through the catheter but offsetradially from a central axis of the catheter.
 12. The method of claim 1wherein the intravascular blood pump further comprising a pressuresensing element configured to sense pressure proximate the intravascularblood pump, the pressure sensing element comprising at least one of apiezo-electric pressure sensing element and a strain gauge.
 13. Themethod of claim 12 wherein the pressure sensing element furthercomprising a fluid column extending through the catheter.
 14. The methodof claim 12 wherein the pressure sensing element is used to determine adifferential pressure.
 15. The method of claim 1 wherein theintravascular blood pump system further comprising a rotor shroud, aportion of the rotor shroud having an outer diameter matching an innerdiameter of a proximal portion of the cannula.
 16. The method of claim 1wherein the intravascular blood pump system further comprising a rotorshroud disposed about the rotor and wherein a proximal portion of thecannula is disposed about a distal portion of the rotor shroud, thedistal portion of the rotor shroud having an outer diameter smaller thana diameter of a more proximal portion of the rotor shroud, at least aportion of the rotor shroud having the same outer diameter as thecannula.
 17. The method of claim 1 wherein the intravascular blood pumpsystem further comprising a rotor shroud, motor assembly and a drivecable, the drive cable at least partially disposed within the catheter,wherein the motor assembly and drive cable are configured to drive therotor, wherein the elongate lumen is proximal to the cannula and themotor assembly is configured to remain external to the patient, andwherein the intravascular blood pump system comprising a dualconstruction arrangement whereby the rotor is configured to be dockedwithin the rotor shroud.
 18. The method of claim 1 wherein the elongatelumen runs longitudinally through and is an integral extension of a wallof the cannula.
 19. The method of claim 1 wherein the elongate lumen isa side lumen extending longitudinally but offset radially from a centralaxis of the cannula along at least a portion of the cannula.
 20. Themethod of claim 1 wherein the elongate lumen is adapted to guide theguide wire through a distal end of the intravascular blood pump system.21. The method of claim 1 wherein the elongate lumen is shorter inlength than the cannula lumen.
 22. The method of claim 1 wherein theintravascular blood pump system further comprising a distal tip memberat one end, the distal tip member comprising a stem portion, extendingdistally away from a distal end of the cannula lumen, and a curved tailportion located distal to the stem portion.
 23. The method of claim 1wherein the intravascular blood pump system further comprising a pigtailshaped distal tip member at one end.
 24. The method of claim 1 whereinthe intravascular blood pump system further comprising a J-shaped shapeddistal tip member at one end.
 25. The method of claim 1 wherein theintravascular blood pump system further comprising a fluid delivery pumpconfigured to deliver purge fluid through the purge lumen towards theintravascular blood pump at a pressure that is both sufficient to avoidclotting of the patient's blood and that is higher than a blood pressureof the patient adjacent the intravascular blood pump.
 26. The method ofclaim 1 wherein the elongate lumen is at least partially disposed withinan outer surface of the cannula.
 27. The method of claim 22 wherein theelongate lumen is located proximal to the distal tip member.
 28. Amethod for providing left-heart support using an intravascular bloodpump system, wherein the intravascular blood pump system comprises: anintravascular blood pump adapted to be guided to a predeterminedlocation within the circulatory system of a patient by a guide wire andconfigured to provide left-heart support, the intravascular blood pumpcomprising a rotor having a rotor hub tapering in the distal directionand a rotor shroud at least partially disposed about the rotor hub, atleast one blade extending radially outward from the rotor hub, a distalend of the hub extending distally beyond a most distal portion of the atleast one blade; a catheter coupled to a proximal end of theintravascular blood pump, a purge lumen extending through the catheter;a cannula coupled to a distal end of the intravascular blood pump, aportion of the rotor shroud having an outer diameter matching an innerdiameter of a proximal portion of the cannula, the proximal portion ofthe cannula disposed about a distal end of the rotor shroud, one or morefirst ports and one or more second ports establishing fluidcommunication between a cannula lumen and an exterior region of thecannula, wherein at least one first port is located in proximity to therotor and at least one second port is spaced apart from and locateddistal to the at least one first port; an elongate lumen associated withthe cannula and sized to slidably receive the guide wire and dimensionedsuch that the guide wire passes slidably and coaxially through theelongate lumen, the elongate lumen is sized smaller cross sectionallythan the cannula lumen, both the elongate lumen and the cannula lumennot extending through the rotor huh, the elongate lumen adapted to guidethe guide wire through a distal end of the intravascular blood pumpsystem, the elongate lumen is at least partially disposed within anouter surface of the cannula; a housing connected to a proximal end ofthe catheter; and first and second conduits each connected to thehousing, at least one of the first conduit and second conduit in fluidcommunication with the purge lumen, the housing remains outside thepatient while providing left-heart support; wherein the method forproviding left-heart support comprises the steps of passing the guidewire through the patient's femoral artery such that a distal end of theguide wire is positioned in the left ventricle of the patient's heart;placing the guide wire through both the cannula and the elongate lumen,wherein the guide wire enters the intravascular blood pump systemthrough one end of the elongate lumen and exits the intravascular bloodpump system through an opposite end of the elongate lumen, the guidewire not passing through the rotor hub or the catheter; advancing thecannula into the patient using the guide wire and positioning thecannula across an aortic valve of the patient such that a distal end ofthe cannula and the at least one second port are positioned in the leftventricle and a proximal end of the cannula and the at least one firstport are positioned in the aorta; passing purge fluid through one of thefirst and second conduits, through the housing and purge lumen to theintravascular blood pump; measuring pressure adjacent the intravascularblood pump; and spinning the rotor so as to pump blood from thepatient's heart into the at least one second port through the cannulalumen and out the at least one first port to provide left-heart support.29. The method of claim 28 wherein the intravascular blood pump systemfurther comprising a fluid delivery pump configured to deliver purgefluid through the purge lumen towards the intravascular blood pump at apressure that is both sufficient to avoid clotting of the patient'sblood and that is higher than a blood pressure of the patient adjacentthe intravascular blood pump.
 30. The method of claim 28 wherein theintravascular blood pump system further comprising a motor assembly anda drive cable, the drive cable at least partially disposed within thecatheter, wherein the motor assembly and drive cable are configured todrive the rotor, wherein the elongate lumen is proximal to the cannulaand the motor assembly is configured to remain external to the patient,and wherein the intravascular blood pump system comprising a dualconstruction arrangement whereby the rotor is configured to be dockedwithin the rotor shroud.